Throughout the heat wave, temperatures will be about 15 degrees above normal.
Wednesday’s possible records
On Wednesday, record highs at all three Washington-area airports will be in reach as temperatures soar into the upper 80s and lows 90s.
The high resolution NAM model forecasts a high of 92 at Reagan National Airport, which would match the record set in 1974.
Dulles International Airport’s existing record of 89 from 1986 has a very good chance to fall.
The record high of 93 degrees from 1896 at Baltimore-Washington International Marshall Airport may be toughest to reach.
Thursday’s possible records
Thursday is likely to be the hottest day of the week, with forecast highs of 90 to 95 degrees. However, the record highs on this date are hotter than Wednesday’s and may be difficult to break. They are:
- Reagan National: 96 from 1877.
- Dulles: 91 in 1987.
- BWI: 97 in 1962.
The record high at Dulles has a good chance to fall, but the other two are long shots.
With the air being so warm and humid, nighttime temperatures may struggle to fall below 70 degrees. Records for the warmest low (overnight minimum) temperature for the date are possible at all of the airports. The existing records are:
- Reagan National: 72 in 2015.
- Dulles: 68 in 2015.
- BWI: 68 in 1900.
Friday’s possible records
High temperatures on Friday are forecast to reach around 90 degrees which, while more than 10 degrees above average, should fall below most records for the date (96 at National and 97 at BWI). There’s an outside chance Dulles makes a run at its record for the date: 92 degrees from 1997.
How unusual is this?
As discussed Monday, a May heat wave — defined as three straight days at or above 90 degrees — is somewhat unusual. It happens about once every eight or nine years in Washington, on average.
Since records began in 1872, Washington has posted 17 May heat waves.
Washington’s most recent May heat wave, which lasted the minimum three days, occurred in 2013. The longest May heat wave on record occurred in 1991, lasting seven days — a week’s worth of 90-degree weather.