Heat — District of Columbia, District of Columbia

1999-07-04 to 1999-07-07 · District of Columbia, District of Columbia

Wider weather episode

High pressure sat off the Mid-Atlantic coast from the 4th through the 7th, acting like a heat pump drawing extremely warm and humid air into the region. Temperatures on the 4th through early on the 7th were oppressively hot, and extremely humid conditions added to the misery. These conditions continued until a cold front swept through the area during the afternoon of the 7th, ushering in cooler and much less humid air. The mercury soared into the upper 90s to lower 100s during the period. Dew points were in the lower to middle 70s and heat index values ranged from 85 to 90 degrees. New record highs were recorded at Washington National Airport on the 5th and 6th. The high temperature at National Airport was 99 degrees on the 4th, 102 degrees on the 5th, and 103 degrees on the 6th. As DuPont Circle in Northwest the mercury rose to 100 degrees on the 4th, 103 degrees on the 5th, and 104 degrees on the 6th. Because of the 4th of July holiday weekend, many people were inconvenienced by the oppressive conditions. Those who spent considerable time outdoors or in non-airconditioned buildings were subject to heat related illnesses. Over 525 people, including many tourists in Washington for the Independence Day festivities, were treated for mild heat related illnesses. One hundred fourty people had to be taken to area hospitals suffering from more serious complications. District officials set up free water stations and first aid stations on the Mall to assist visitors and participants. During the late evening fireworks displays, spectators had to brave temperatures in the upper 80s and heat index values in the middle 90s. City officials also opened 5 cooling centers and offered 13 fire hydrants with sprinkler heads for permanent city residents without air conditioning. Over 700 district residents took advantage of the shelters. Even with the available resources, three people succumbed to heat related illnesses. The heat forced the city to cancel summer school classes on the 6th. PEPCO reported record high energy consumption during the late afternoon of the 5th and 6th. The high demand for electrical power blew old transformers, leading to power outages for 1,900 district customers.

Source: NOAA Storm Events Database, event_id 5710604. Narrative written by the NWS forecast office that issued the report.