WASHINGTON — So much for the warm days and cool nights of September. Summer’s oppressive heat and humidity is setting records even as the page on meteorological summer turns.
While Tuesday’s high temperature of 95 degrees established a record for the date at Reagan National Airport, the persistence of the heat into the evening hours was even more significant.
By Tuesday night, the temperature failed to drop below 79 muggy degrees. That temperature was the warmest low on record for the date and month. What’s more, it’s the latest such a warm minimum has ever occurred in a Washington calendar year.
Temperature records for Washington date to the 1870s and are maintained by the National Oceanic and Atmospheric Administration.
It’s the 12th time this year that a record high minimum temperature has been broken or tied. Record-challenging heat has occurred at least once every month except March. Several high temperature records were also broken during the first half of the year.
The low of 72 degrees at Dulles Airport that night was also a record warm minimum, and was the 18th night in 2018 to feature record-breaking heat. Records at Dulles have been kept since 1960.
The warmth in 2018 isn’t just ending late; it began early. On Feb. 21, the record high temperature of 82 degrees was the earliest recorded reading of 80 degrees or greater.
There were no record lows or low maximum temperatures set during the first eight months of the year.
The late heat wave has been capped off with oppressive humidity as well. The National Weather Service said the dew point has been at or above 70 degrees in Washington since last Friday afternoon. At Dulles and other parts of the region, the dew point has been at that level for a week or more. The body’s ability to cool itself is hampered when dew points exceed 70 degrees.
The heat prompted Prince George’s Co. schools to dismiss early on Wednesday. The District activated its heat emergency plan on Labor Day, opening up cooling centers normally reserved for the dog days of summer.
Storm Team 4 is forecasting a respite from the heat but higher odds for rain later this week.