Welcome to Weather Questions, where we answer the questions on your radar.
Welcome into Weathered Questions, the podcast where we answer the meteorology questions on your radar.
My name is Jan Reinhardt, joined by Kai O'Mara, your friendly neighborhood meteorologist here to answer all of your weather wonderings.
Remember, you can get in on the podcast, ask us your questions.
We would love to have those.
We are getting a little lower on those questions here as we're going into the winter season, so feel free to fire us an email.
weathered questions at gmail.com to join in on that conversation.
We would love to know what is on your radar, what you are curious about.
This week, a lot of people, what is on their radar is that it's getting cold.
Or
it
was.
Yeah.
Yeah.
Yeah.
So we're looking at some some frosty days, some chilly mornings.
No, it is still.
classic fall weather, at least for the Midwest, right?
And so we do still have plenty of warm weather mixed in as well, but we did see some temperatures dip down near some dangerous conditions in terms of plants outside over the past weekend.
So today's first question kind of starts to deal with that a little bit, but in somewhat of a more abstract way.
The question is,
Why are the days the same length in September and March, but the temperatures are so different?
Guy, we know how the sun moves.
We've kind of talked about that before here on the podcast.
Day length, very similar in September and March, but the temperature difference drastically different, I would argue, usually.
What's going on?
Oh, yeah.
Yeah.
And in fact, we think about the way that our winter records go.
September, we don't really have any big winter storms that happen in the Midwest.
It's just a little too early.
But in March, we know very well that's very different.
So this all comes down to Earth's energy budget and how the sun operates within this entire realm that we live in.
So in order to get your daytime highs, the sun
has to heat the ground, and then the ground heats the air above it.
It's not as simple as the heat lamp, Jan, that we had in the high school cafeteria to keep the chicken patties warm.
That's not how this works.
Because that same heat lamp would keep that same chicken warm, whether you're in the chemistry room, whether you're in the library, whether you're in the lunchroom, because it's an equal source of heat and that ground is different, that temperature is different wherever that platter is.
Now, take that same heat lamp,
and put it in the freezer where all of a sudden maybe your plate is a whole lot colder than what it was.
So in order for us to say hit a daytime high of 75 in September, the sun needs to heat the ground.
The ground heats the air above it.
Why is the ground so much warmer in September?
It's because we are coming out of summer.
It's temperature lag.
That's also why
We fill up the swimming pools.
If you have a backyard pool in June, it takes a few days to get warm.
There's mass there.
So we're coming out of a warm period, which means you can actually keep the warmth a little bit longer, which is why even despite the shorter days, we can still get temperatures in the 70s and 80s.
Whereas in the wintertime, oftentimes we don't get our coldest days until we've already started gaining daylight again.
And it just shows how important that ground is to everything.
And then on top of that, what if we put snowpack on it?
Boom.
You're toast.
It's like, yeah, you're not going to warm up now.
Yet the sun is the same angle as it would be on Halloween, right?
In February.
So that's the big difference, in my opinion.
that we see temperature so drastically different despite the fact that the daylight's the same.
What's the X factor?
What's the difference when you look at the data?
The ground is cold.
That's your biggest difference.
It's the ground temperature.
Yeah.
And you noted really briefly there, like, you know, how your swimming pool, right?
How that water takes a long time to warm up.
And I think that's an important consideration for this.
It's not something maybe that people who are outside of
Physical science or meteorology consider a lot, but it takes a lot of heat and energy to warm up water We see this in in something like hurricane season where Hurricane season goes into the end of November and I think
kind
of in our heads We we think oh well hurricanes.
That's like a that's like a summertime thing.
That's a hot thing That's a tropical thing and
it
is but because the water
Warms up through the summer and then stays warm enough into late November, typically, that we could still be getting those hurricanes and then it starts to cool down enough, but we don't have hurricanes season, you know, on the flip side of the summer solstice starting that much earlier because it's cold.
The other thing I like to compare this to, because again, still that may be a little abstract to be considering,
Think of just having a saucepan on your stove, right?
When you put it on your stove, it's room temperature, it's quote unquote cold compared to what that stove will be.
You put it on the stove, it starts to warm up, it warms up.
Obviously, yes, we're talking about like conduction and all of that stuff with metal, but like when you turn off the stove, when you turn off that burner, it stays hot for a while.
It doesn't just instantly cool down.
And that's basically what's going on with
with the sun heating the earth, is that it takes time for that to happen.
Yeah, we call that temperature lag.
We try and be very simple in the weather world, even though a lot of our science is really...
complex when we try and do the out-facing stuff to the public, it's called temperature lag.
For a reason, you know, it lags behind about 60 days, sometimes 90 days, depending on, you know, what kind of extreme you're talking about.
So that gets us to another one, Jan, that kind of confounds the mind a little bit.
And that's one of the big pillars of weathered questions is, what is something, you know, when you're driving around and you see something, you go, what, what the heck?
Like, how is that even happening?
That's why you and I exist.
in this world to answer that question.
We're
here for you.
This past weekend, I had one of the nicest mornings I think I've ever had so far this fall.
We had no wind.
Temperature was 30 degrees.
A layer of frost out there.
Bear and I went for a walk.
We went up to Norwich Park.
We did a full lap.
But of course, we're driving and what do I see?
Norwich pond is steaming.
I mean, it looks like somebody's cooking mac and cheese in there, all right?
It is steaming.
So here's the question.
Jan, why is the lake steaming on a cold morning?
Why on earth would that lake steam with a temperature above it at 30 degrees?
That's the question.
Allow me to take everybody listening here on a little time travel, about two minutes in the past,
where
we talked about water, how it takes
a lot of time to change the temperature of it.
That's what's going on here.
You've got a body of water, you've got a lake, you've got a pond, you've got a river, and it is a warmer temperature relative to the ground and the air around it because
As we're getting into these cooler weather months, the air is more arid.
It's drier, less moisture there.
It cools down faster.
The water, again, takes more time to change that temperature.
And so what it really boils down to is that the water is warmer.
The air, again, the land, the air over it.
Land around it air over it.
Sorry.
Hopefully there's not land over your water.
You've got a problem there But you've got a temperature difference is what we're getting at here.
So Basically the the warm lake water is evaporating up And and you're seeing that that fog that that kind of difference in in temperature through that evaporation
maybe even in some condensation there, but basically change in state of your water in your air versus the water in that lake or that pond that you are seeing that happening over.
So
yeah.
Kind of funny that
you mentioned that seeing that.
Oh yeah.
My husband just same morning, right?
Two hours away, but same morning.
He was looking outside kind of in the same area and he's like
Is the grill on?
And I think because there was some frost that was starting to evaporate and stuff.
And so you could see like those little kind of puffs coming up.
But yeah, similar, similar change there, right?
And what it does is this is just really a visual of physics at work is what it is.
Because I think we learn from a really early age that warm air holds more water.
then cold air does.
We know this just by how many times do you have to apply ChapStick in December versus July?
You know, it's really— I did buy new
ChapStick this week.
Right.
It's that easy to understand, right?
Warm air holds more moisture.
It doesn't mean it's always going to do it, but it has the capacity to do it.
And so, we actually call this in the weather world, saturation vapor pressure, three really big words.
But it's a fancy way of saying, how much can that air hold?
So when we have a situation with probably 60 degree lake water, probably, I don't know, I didn't look, but I would guess that given how warm the month has been and all of a sudden you get a cold morning.
Well, now the air above it, okay, that's fine.
It can't hold nearly what the source below it is giving off.
And so there's literally this net flux from the water surface.
up into the atmosphere, it's a net flux between the two pressures.
This is why lake effect snow is what it is.
When cold air moves over the open lake water, that's just on a ginormous scale.
Whereas if it's a farm pond, and it's got a little steam coming off it, number one, you know that's probably the chilliest air of the morning that's pooled right down there.
But number two, it's a great, easy way to tell that, hey, you know, the water is probably warmer than...
than the air above it.
And this could be true for a lake morning.
I saw this happen in the Great Lakes over the summer when we had a cool morning and it wasn't like that cool, but it was in the 50s.
And so we knew at that point, had we settled down, we knew that the lake water was at least 60 at that point because we had that outward flux of vapor pressure going on.
So it's good science when you see that stuff.
And very rarely is it windy when you have a cool morning like that too in the fall.
So it's neat to see.
It's definitely neat to see.
Yeah, you do need similar with regular fog.
We don't get regular fog with strong winds because then the wind just kind of blows it away.
So it does have to be certain conditions.
It's not just going to happen this time of year, no matter what, because of the temperature difference.
There's a few other things that go into it as well.
If it's too breezy, then the wind will just blow it right away.
Yep, mixes it all up, and then the fog's going.
Not a big deal.
Well, we're going to stay on the note of these cooler temperatures here for our trivia question and the remainder of the show.
But let's get into that trivia question today.
Today, very simple.
We are looking for a singular number, preferably in the Fahrenheit vein.
Kai, you can do the conversion.
I only put the answer in Fahrenheit, so I'll
let you
handle that on the
flip
side.
But today's question is, what temperature denotes a hard freeze?
Again, we're looking for one number.
What temperature denotes a hard freeze?
Kai will be back with the answer, maybe in Celsius, definitely in Fahrenheit in just a second.
All righty, I'll give you both because you talked about it Fahrenheit and in Celsius.
Now I will also tell you this.
This is not a dictionary definition.
There will be folks on the farm that have a different definition and that's okay.
That's okay.
We're just gonna give you the generally accepted hard freeze and then we're gonna kind of get into the differences in the terminology.
So the answer we're looking for is 28 degrees Fahrenheit.
And I'm going to call it minus two Celsius just to be simple about it.
I think that's
fair.
Yeah.
And that's a hard free.
So here's kind of the way this whole terminology works because, you know, I don't think the Weather Service issues these anymore.
I believe it's all under the freeze warning blanket, but I think there was a time and I still could be incorrect on this.
Maybe the Southern climates will do this.
You've got freeze warning and then hard freeze warning.
So in my general view and how I grew up,
and how we were kind of really educated through the process in college is you kind of have three different thresholds.
So a frost advisory is issued typically whenever temperatures at night are expected to get anywhere below 40, so 30s mainly.
And the reason for that is because the official temperatures are measured anywhere from about a meter and a half, which is about five feet up, to about two meters, which is about six and a half feet up.
the actual surface of the ground can be much colder and if it's 38 degrees that official observation point it might be more like 32 on the ground and then you get a few ice crystals to form and so you sometimes get wording called patchy frost or patches of frost and in this particular instance you'd see a frost advisory come out.
Typically what that means for gardeners is cover your plants but they'll probably be fine as long as they're covered.
Now, freeze warning is different.
So an actual freeze is just simply getting that official temperature to 32.
That's it.
It can be windy as heck.
You might not see any sort of ice crystals as long as that official temperature gets to or below 32 for the first time that fall season.
And we're just talking about fall.
The spring is the opposite, but we're just talking about fall because that's when this is being put together.
Just hitting that 32 mark, that's a freeze.
Can a plant survive that?
Absolutely it can.
If it's covered,
Sure.
Hard freeze.
Now we are, let's just think about it this way.
If you accidentally hit the stem of a plant, there's a lot of water in there, like a ton of water.
I mean, you only have to put your hands on a tomato plant for a second and then you smell like a tomato the rest of the night because there's so much moisture in that stem.
And, you know, if you are out there and you're picking your last few tomatoes of the season and you want to just sacrifice one of the mini stems you have and you cut it or you tear it, you'll see there's a lot of water in there.
So the general feeling is that 28 degrees for several hours is enough exposure to actually freeze the water in the veins of the plant.
Now you've killed it, basically.
Now you've killed it.
And so that's what we consider a killing freeze.
When I was growing up,
The general rule of thumb was four hours of 28 or colder.
That's just what I was taught.
I'm not going to debate somebody if they say it's actually three hours at 27.
I don't care that much about it.
The bottom line is 20s for several hours is probably what's going to be a killing freeze or a hard freeze.
So we call it a hard freezing point.
To be correct.
But in the reality of it, you know, if you talk to the gardening community, our plant's going to die.
Is this going to be enough to kill my plants?
Now, Jan, we can expand on this.
You can water the heck out of your plants the afternoon before a freeze.
And then when you cover them, that water in there actually will keep the temperature up for you a little bit.
It'll help you at least get to that point.
Part of me also says, right, right.
And then part of me also says, if we get to Halloween and you still have stuff that's producing, especially in Iowa,
You've done a pretty good job.
It's pretty tough to save it in November because now The normal lows in November start to plummet deep into the 20s and at that point and if you go and visit a plant After it's had a hard freeze the stems are dry.
It's it's done.
It's done.
So I Don't know if it's different in your world, but in my world, that's kind of what I denote a hard freeze to be
Fortunately, we share the same world.
That's good.
But I mean, it's a valid question.
It's a valid question to discuss.
It
is.
And to your point, yes, some people will say, no, it's not till 27.
No, it's not till 27.
We're fighting over one degree here.
And if it's one hour versus two hour, I guess, to your point, four hours versus three hours or something like that.
it's a period of time, an extended period of time, several degrees below that freezing point.
That is the main thing that we're looking at here.
But I do always find it entertaining when, similar to this, you know, most recent event where we get, we, a lot of times we kind of approach that freezing point where it's like we get some temperatures in the, in the mid to lower thirties.
And, and so we have those
frost advisories, and then we get the freeze warnings.
And so we get all of the first messaging of, well, cover your plants, cover your plants, and then bring your plants inside.
And then it's, you know, it's the freeze.
And this time we kind of jumped straight into the freeze side of things.
And I always find it very interesting when people still think that covering their plants is going to protect them from 27 degree temperatures.
that
little bed
sheet isn't going to do much.
Right.
It gets pretty difficult.
It gets pretty difficult.
Especially
when you're talking about tomatoes, which are tropical plants, they're
just not
going to they're just not going to make it.
You know, you're
hard.
You're super, super high water
content.
Yeah.
Yeah, exactly.
But yeah, I I I did cover my tomato plants in hopes that maybe it would only get down to like 34 or something.
No, no dice.
Those flowers are zapped.
Even though-
I will tell you, I love gardening.
I've never covered my plants in the history of having plants.
Because to me, seriously, to me, I go, you know what, it's done.
It's nature's call.
It's nature's way of saying I'm done.
And I will tell you what, by the time we get to the end of September, I have had enough tomatoes that I'm good.
I really am.
I'm OK.
And if the basil gets a little freeze dried, eh.
It's all right.
Still tastes good.
But then that just signifies to me, all right, I should naturally start switching over to Crock-Pot kind of stuff now.
So I just leave that alone.
Yeah, I just leave it alone.
I don't cover it.
I just don't care that much.
But I think that also just goes to the territory of having two kids that are super busy and just trying to figure out what day of the week it is half the time is a big battle.
So it could just be a parent thing.
All right.
Okay.
Now we're on the gardening topic now.
So I got to squeeze one more question.
Are you the kind of person who like, okay, that freeze or frost is coming, you're not going to cover your plants.
Do you take off all the tomatoes or do you just like say like whatever's on the plant is done?
And by all the tomatoes, I mean not just the red ones that are ready to eat, but the ones that like still need to sun ripen.
No, it depends on the year.
It depends on the year.
If we can go out and grab some good ones, then I will.
But then otherwise, there was one time I went out there after a frost and I tried one anyway.
It was still good.
So I mean, it was, we rebounded quickly.
So I guess it's all right.
But who knows?
I mean, if you just have a touch of frost and it's a really thick tomato plant and maybe there are some tomatoes under the main leaf, maybe they didn't get hit by it, you know?
So it's very possible.
Plants do have that built-in protection.
Leaves are great at that.
Yeah.
Oh, yeah.
Definitely.
Yeah.
I always strip like when it this this one off, I didn't take them all off.
But as we get closer to the multiple nights in a row, I take all the tomatoes off and throw them on a sheet pan and just let them sit by the sun for a while.
And I've still got tomatoes ripening into November end of November.
Thanks.
Past Thanksgiving.
It's
great.
Yeah.
That's awesome.
Don't waste them.
No, well and going back into kind of like location location that we just discussed I'm just gonna toss this one at you because we're we're getting close to the end of the podcast So when Bear and I were outside on that that morning when we were walking we noticed some interesting patterns in the way the frost had developed Wide open thick totally uniform for us under trees hardly any
The meteorological explanation for that, Jan, is what?
Well, I think we talked about this way back when.
I couldn't
tell you what
episode, but you might recall a conversation where we talked about snow melting around trees first as compared to other parts.
You've got a whole yard, one little tree in it, and all the snow's gone around the tree, but everything else is still snowy.
Same concept here.
Essentially trees have, they are radiating heat outward, whether or not you, you know, but they have, they have an energy, basically a thermal energy that they are radiating.
And so that can kind of influence things that, you know, cold.
frost, snow, things like that from being able to stay in that area right around it.
So you'll notice that it is generally very uniform around the tree, that it is kind of melting off.
So, yeah.
And, you know, another thing that we've talked about before as well, but to bring that concept back and help you kind of start, you know, tying things together.
Tree bark tends to be a very dark color tends to absorb more energy as well.
So then as as you have the sun heating things up and and helping warm the world That is also playing into it there where the darker things, you know, if you had if you had a
I don't know, a really dark colored tree bark and a lighter colored tree bark, the darker colored tree bark might have a larger area around it that does not have things freezing because of that coloring, because of the energy that it is absorbing and then reemitting out into the world.
So yeah, that's
what's going
on there.
And then the reemission port that you just got into, something we called long wave radiation.
So short wave is the stuff from the sun.
Longwave is the stuff that's cooling and everything emits radiation.
If you grab a clothespin from the laundry room, the clothespin is emitting longwave radiation.
You don't really know it, but it does.
It does.
Now everyone's going to throw their clothespins
out.
Take a pan of brownies out of the oven and set it outside.
In the wintertime, you're going to actually see it happening, okay?
It's going to be emitting radiation.
So when the land cools,
If that long wave radiation is going out from the land and it's actually underneath a tree canopy, those leaves can absorb that and then reabsorb it in all directions.
And so not only do you have the heat of the tree and the water within the trunk from the day itself, now you've also got the long wave kind of getting messed up because if there's leaves on the trees, it can actually kind of protect it.
in a way.
So not only do you get it around the trunk, but it actually, as you go around the outside, you'll notice that the frost has a harder time penetrating, especially for kind of in those marginal situations, like 28 higher.
If you're down at like 20 degrees, eh, you're going to get it no matter what.
But in those marginal cases where it's upper 20s, lower 30s, watch for that next time.
And that's the science behind it.
It's really quite cool.
It's neat.
Yeah, it really is.
Well, that
brings us here to the end of another episode.
So if you picked up on something, please let us know about it.
We want to hear your questions.
We want to know what you're wondering about.
Yes, and please think about winter.
Please think about wintertime questions.
Think about why is it that that snowfall range is so big?
Why is it that we've got people on the internet scaring us?
Can we actually have a winter outlook that's accurate?
Is it possible?
What could El Nino do for our winter?
Think about that kind of stuff in the back of your mind and we can get those answers all put together for you.
Whatever is on your mind.
That's why Jan and I are here.
You can send us an email weatheredquestions at gmail.com to join in on the conversation.
In the meantime, I hope you learned something today.
Tell your friends about it.
Tell your family about it.
And until next time, stay safe.
