(This report, originally posted Tuesday, was updated Wednesday afternoon.)
Both Tuesday’s and Wednesday’s temperatures are some 25 to 35 degrees above normal. Capital Weather Gang’s Ian Livingston notes the high temperatures of 78 and 82 on Tuesday and Wednesday mark the warmest back-to-back readings in winter ever observed in Washington.
Yesterday (78) and today (at least 81) are the warmest back-to-back high temperatures during winter (Dec-Feb) in DC. Previous was 78 and 79 Dec 6-7 1998. Records date to 1872. @capitalweather pic.twitter.com/xkrES2IOdT— Ian Livingston (@islivingston) February 21, 2018
Wednesday’s record warmth
Temperatures Wednesday afternoon sprinted into the upper 70s and low 80s.
Reagan National Airport, Washington’s official measurement site, surged to 82 degrees crushing the previous record of 75 from 1953. Dulles Airport sailed past its previous record of 70 from 1997, hitting 80 degrees. Baltimore-Washington International Marshall rose to 79, cruising past the prior record of 74 from 1930.
The 82 degrees at National ties the second highest February temperature ever observed since records began in 1872, either at the airport or at 24th and M St in the District, where measurements were taken prior to 1945.
At 80 degrees, Dulles Airport logged its warmest temperature on record for the month of February, passing the previous mark of 79 degrees, set Feb. 17, 1976.
BWI’s 79 degrees ties for the second warmest February reading in Baltimore’s temperature history.
Winds from the south kept pumping in warm air Tuesday night, so temperatures fell only into the 50s throughout the region Wednesday morning.
All three airports had their highest low temperatures on record for the date through 7 a.m.:
- National’s low of 56 was higher than the previous record of 51 from 1954.
- Dulles’s low of 59 was way higher that the previous record of 45 from 1981.
- BWI’s low of 52 was higher than the previous record of 49 from 1981.
Dulles’s low of 59 was not only the warmest for the date but also for the entire month of February, several degrees above the previous record of 55, set Feb. 17, 1976.
(Note that a cool front edging toward the region Wednesday night might bring temperatures down enough to prevent these records from holding.)
Record highs set Tuesday
The wedge of cool air that trapped temperatures in the 40s Monday collapsed, and temperatures Tuesday afternoon soared into the 70s.
Summary of record highs today: No new record warm lows due to temperatures this morning. Record highs broken today at DCA/IAD and tied at BWI (unlikely to rise higher). Both the record high and warm low for Feb 21 in jeopardy. pic.twitter.com/UFhS8JsEgN— NWS Baltimore-Washington (@NWS_BaltWash) February 20, 2018
Reagan National and Dulles International Airports rose to 78 and 77 degrees, breaking their previous respective records of 76 degrees from 1930 and 70 from 1971. BWI tied its record high of 76 set in 1930.
The high of 78 at National tied for the fifth-warmest February day on record in Washington.
Second year in a row with multiple days of 70-degree warmth in February
February is starting to look like a repeat of last February, when we also witnessed anomalous warmth late in the month. National posted four days above 70 between Feb. 19 and 26, 2017:
- Feb. 19: 71
- Feb. 23: 75
- Feb. 24: 77
- Feb. 25: 75
So much warmth so soon brought the unwelcome effect of an early uptick in pollen levels and a premature start of the growing season. Many early bloomers, such as the cherry blossoms, were then damaged when a hard freeze came in mid-March.
This February’s warmth hasn’t been quite so extreme, but we’re likely to post our third 70-plus-degree day in a week on Wednesday (last Thursday it hit 74). Over the upcoming weekend, we could again be near 70.
A record high pressure or “heat” dome is responsible for the warmth
The record-warmth predicted through Wednesday is the result of a historically strong area of high pressure or heat dome positioned off the Southeast coast.
There's been some confusion about the 500-hPa percentile plots. To clarify, these are the forecast 500mb heights relative to a 3-week centered climatology. "Max 5 rad" indicates the forecast values exceed the record at that location and in a surrounding 5 degree radius. pic.twitter.com/6xa1Ra456k— Tomer Burg (@burgwx) February 20, 2018
The clockwise flow around this heat dome is circulating abnormally warm air up the entire Eastern Seaboard.
It will drift slightly east Thursday and Friday, allowing cooler air to sink into our region. It may drift west and become reestablished this weekend, although its exact position is still uncertain.
80-degree warmth milestone adds to a long list
This record earliest occurrence of 80 degrees in Washington adds to an extensive list of warm weather extremes set since 2010. Collectively, this list offers a compelling indication that the area’s climate is changing profoundly due to both urbanization and the build-up of greenhouse gases in the atmosphere.