Dan DePodwin breaks down the historical averages of spring's final freeze across the U.S. and when the Great Lakes and Northeast can expect their final freeze before warmer days take over.
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00:00We want to start off, when does the frost and freeze risk typically end, and then how does it vary across our country?
00:05In terms of the sunflower seed from your son, Ari, I guess it depends where you live, right?
00:11If you're in the parts of the northeast in Great Lakes, it can be a difficult time of year here in late April to plan.
00:16Looking at the graphic here, that shows from the eastern two-thirds of the country, basically,
00:20and we're clear, basically, in the southeast in Tennessee Valley, a lot of the plains,
00:24we're no longer dealing with sub-freezing temperatures at night.
00:27The western U.S. varies considerably depending on if you live in a mountainous area or in a valley,
00:31so it's more difficult to depict on a map, so know your local climate there in the west.
00:36But in the eastern U.S., the risk here is basically across the northern third or so of the eastern United States here for the next two to three weeks.
00:45And these are all historical averages.
00:47We know that there's some times where it's super early or super late, so can you share some of those records in some of our bigger cities?
00:53Yeah, it really depends where you live, obviously, but there's some really early last freeze.
00:56For instance, in Washington, D.C., February 27th, but the latest, there was a freeze there in late April.
01:05But you go farther west into the Ohio Valley, in some cases Detroit and Indianapolis, there can be a freeze in late May.
01:12And farther out into the western United States, Denver, Colorado, even the record latest freeze there is June 2nd.
01:18Flagstaff, Arizona, at a high elevation, even had a freeze on July 8th one year, many years ago.
01:23Wow, I love looking back at that data, just kind of fascinating, and to know that, yeah, there's quite a range.
01:29And speaking of the range, you know, if you use the Accurator app, Accurator.com,
01:31and folks are looking at kind of an hourly temperature or the overnight temperature,
01:35there can be a little bit of a vary, of course, for where the plants actually are.
01:39Yeah, certainly the case where the plants are at the ground level,
01:42and you can sometimes be five, even six, seven degrees cooler at the ground level there,
01:48and then five to ten feet above the ground level where the temperature is typically measured.
01:52So even in a case of your low temperature, it's going to be 34, 35 degrees, if that's the forecast.
01:57You can expect it to be a couple degrees cooler at ground level where the plants are.
02:00So even those cases, it's good to either bring sensitive vegetation inside or protect them overnight.
02:05That's a good tip.
02:06All right, let's go forward here as we wrap up April.
02:09And we head into May, we could be talking about some frost and freeze risks here,
02:13even as early as Thursday morning this week.
02:15Yeah, later this week, a chilly air mass.
02:17After a warm day here Tuesday, by Thursday morning, a very chilly start across the interior portions of the northeast,
02:23including the Green and White Mountains of New England, as well as the Adirondacks,
02:25are going to be a freeze and frost in those spots, pretty typical for this time of year.
02:29And if we look ahead even to the weekend, it's going to be chilly again,
02:32another blast of some chillier air as we start May,
02:35with temperatures well into the, or falling into the 20s and 30s across the interior northeast
02:39and parts of southern Canada there.
02:40So definitely still some blasts of chilly air over the next couple weeks in the northeast
02:46can cause frost and freeze.
02:48And we like to highlight our team, such a large team here, many different departments,
02:51including the long-range team.
02:53And this next graphic gives some really additional information here about what we can expect in the coming weeks.
02:59So how does our team create this long-range forecast?
03:01Yeah, so we look at a lot of different forecast models,
03:03not just the short-range models that predict the next week or so, but two, three weeks in the future.
03:08We look at the weather patterns across the globe to see how that's going to influence the weather in the United States,
03:14and there's different tools we use to do that.
03:16And we look at historical years, sort of similar years,
03:19to get that forecast out one to two months to see what may happen.
03:22And in this case, we think that this area shaded in pink
03:24is where we have a higher-than-average chance of a frost that's later than average.
03:28So in this case, mid to late May,
03:30we can still see some frost and freezes here across the northern portions of Pennsylvania
03:33through New York into New England.
03:37But the coastal east coast here from Boston down to D.C.
03:40should be in the clear here from a frost-freeze perspective after this weekend.
03:43All right, so final question.
03:44When can I plant my sunflower, Dan?
03:47I think here in central Pennsylvania, probably Mother's Day is a good weekend for planting.
03:52Oh, how beautiful.
03:53It's like they planned that on purpose.
03:55We love daycare.
03:55All right, ACCUrether, Senior Director, Forecasting of Operations, Dan DePodvin,
04:00thanks again so much for joining us.
04:01You're welcome.