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Posted at 12:15 PM ET, 03/30/2010

The first March without a freeze

By Jason Samenow

* Sunny and warm days coming: Full Forecast *

march2010-lows.jpg
Actual low temperatures this March at Reagan National Airport (DCA) with average lows and 32 degrees as reference points.

After our uber-wintry December, January, and February -- March has been notably tame. When the clock strikes midnight Wednesday night (Thursday morning), the entire month will have passed with the mercury failing to drop below 33 degrees at Reagan National Airport (DCA), Washington, D.C.'s official observing station. When was the last time this happened?

It hasn't. There has yet to be a March in the books where the temperature has not reached freezing in Washington, D.C. That's in nearly 140 years of record-keeping (note that prior to June 30, 1945 dating back to 1872, official records were kept at Weather Bureau "City Office" at 24th and M St. NW rather than Reagan National Airport).

There have been 2 cases where there has been just 1 day with freezing (or below) temperatures in March; March 5, 1945 (32F) and March 1, 1973 (31F).

Just because this March will almost certainly go down as freeze-less, we're not completely out of the woods for freezing temperatures.

Keep reading for a discussion of freeze prospects in April...

Based on a search of 138 yrs (1872-2009) of minimum temperature data (for DCA and 24th and M St. observing stations):

*The "average" date of the "last occurrence" of 32F is April 2nd.

*The "earliest" date of the "last occurrence" of 32F is March 5, 1945 (one of 2 March months that had only 1 day of 32F) which almost certainly will be replaced by February 27, 2010

*The "latest" date of the "last occurrence" of 32F is April 29, 1874 (though this was prior to considerable urbanization, any greenhouse warming and at 24th and M, rather than Reagan National)

So history tells us a freeze could still happen. But with the warm weather in the pipeline through the weekend, it's looking pretty unlikely. As April wears on, reaching 32 becomes harder and harder...

[Note: While DCA hasn't recorded a freeze in March, two National Weather Service co-op stations in the District have recorded multiple freezes. The Dalecarlia Reservoir has reached 32 or lower on 5 occasions (6th, 7th, 9th, 27th, 28th) and the National Arboretum on three occasions (6th, 27th, 28th)]

Special thanks to Steve Zubrick, Science Operations Officer at the National Weather Service Office in Sterling for providing much of the data used in this post...

By Jason Samenow  | March 30, 2010; 12:15 PM ET
Categories:  Local Climate  
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Next: PM Update: Warmth knocking on the door

Comments

Yet another in the long string of reasons why DCA should not be used as the measurement of record for Washington, DC.

Posted by: vtavgjoe | March 30, 2010 11:16 AM | Report abuse

Looks like low temps dropped to 32F or below six times at Dulles and five times at BWI so far this month.

Posted by: Ann-CapitalWeatherGang | March 30, 2010 11:43 AM | Report abuse

CWG - is there a date somewhere between the "average" last frost (April 2) and "latest-ever" last frost (April 29) that's good to use as a rule of thumb for gardening? Like a date for "pretty gosh-darn sure there won't be another frost," or "hasn't been another frost past today since 1950," or odds like 75% or 90% or something? Thanks!

Posted by: jantos2 | March 30, 2010 12:12 PM | Report abuse

This also means that the 28-inch Knickerbocker snow in 1922 was also recorded at 24th and M, NW. Snow accumulations at DCA could have been 20 inches or less. Reagan National was swampland along the Potomac at that time.

Posted by: Bombo47jea | March 30, 2010 12:13 PM | Report abuse

Channel 9's two new TV mets...Devon Lucie replaces Tony Pann, who moved to Baltimore, and Lynette Charles replaces Kim Martucci...it appears they didn't abolish any positions, but hired replacements. It still seems as though a number of viewers still don't agree with the decision not to renew Kim Martucci's contract.

Posted by: Bombo47jea | March 30, 2010 12:24 PM | Report abuse

The DCA thing is somewhat unfortunate but I don't think it's totally unrepresentative. Through yesterday, March was running +4.7 at DCA and BWI and +6.0 at IAD. So, it's not like that location is running super warm or anything compared to the region as a whole.

Posted by: Ian-CapitalWeatherGang | March 30, 2010 12:24 PM | Report abuse

That's BS. I'm in Tenleytown, and there were puddles with icy surfaces in my yard this past weekend.

Posted by: Langway4Eva | March 30, 2010 12:42 PM | Report abuse

I was on the Mall on saturday morning and there were thin layers of ice on all the puddles.

Posted by: Tom8 | March 30, 2010 1:10 PM | Report abuse

Hi-

I live downtown near the Convention Center...is there an automated weather station at the DC Convention Center that's posted online...if not, what's the closest one to that neighborhood?

Posted by: dcbat | March 30, 2010 1:41 PM | Report abuse

@jantos2

We have the frost info somewhere (just have to find it), and we'll follow-up on that in a future post.

Posted by: CapitalWeatherGang | March 30, 2010 1:54 PM | Report abuse

dcbat,

I don't know DC well enough but I googled "weatherbug washington dc" and came up with this:

weather.weatherbug.com/DC/Washington-weather/weather-station.html?zcode=z6286

It is the closest one to you (I think)

Hope it helps

Posted by: worldtraveler83 | March 30, 2010 4:27 PM | Report abuse

I second Jantos' comment!
I have been putting out my herbs outside during daytime and then take them back inside at nighttime to protect against the frost. Back and forth, back and forth (with numerous attempts to escape by my cat) and I am pretty ready to leave those green kiddos outside permanently, so I will keep an eye out for your post about the last possible frost!

Posted by: SanDieganLostinDC | March 30, 2010 6:26 PM | Report abuse

Keep in mind that temperatures are taken at a height of around 5 feet above the ground. On a clear night with little wind it can be above freezing at 5 feet but below freezing at the ground itself.

Posted by: dcawx | March 30, 2010 6:43 PM | Report abuse

dcawx - I think you mention the standard weather station height (isn't it 2m = 6.56ft?) to explain why some frost has been experienced on suburban grassy surfaces & cars several times in March, while DCA recorded no sub-freezing temps -- am I right?

Posted by: Camden-CapitalWeatherGang | March 30, 2010 8:46 PM | Report abuse

@jantos2 - as a gardener in multiple areas, I'd have to say that you just have to know your own microclimates - even the best guide from meteorologists won't cover all the bases. I live in 20170, and last I checked, have at least 2 climate zones in my yard.
That also means that while it may not be safe to plant out tender seedlings at the far edge of the yard, I can put things out on my concrete patio next to the house, and the combo of shelter and retained heat will offset a degree or two of frost.
BTW, my thyme, lavender, sage have already been out, and the rosemary goes back out today!

Posted by: fsd50 | March 31, 2010 1:19 PM | Report abuse

"*The "latest" date of the "last occurrence" of 32F is April 29, 1874 (though this was prior to considerable urbanization, any greenhouse warming and at 24th and M, rather than Reagan National)"

Yeah...I'd be interested in the "modern" record for this when it comes to gardening. Do we have the latest frost at DCA? Since we all seem to agree that is arguably the warmest place in the area, that would be the data point to look at, right?

Posted by: amaranthpa | April 1, 2010 11:07 AM | Report abuse

The comments to this entry are closed.

 
 
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