Excessive Heat comes as no surprise the outlook below, but the Nationwide Climate Service has issued an extreme heat watch for the Washington area Friday and Saturday for heat index values of 110 to 115 degrees between the hours of 11 a.m. and 9 p.m. According to the Weather Service, such a watch is issued when “a prolonged period of dangerously high temperatures is possible.”
Hundred-degree temperature weather is in the forecast for Washington city for the first time since 2016, as punishing, long-duration heatwave peaks over the area Friday into the weekend.
Today’s brutal combination of heat and humidity, in which heat index values have exceeded 105, is just a preview of even more oppressive conditions in the best way. The warmth index, which is a measure of how sizzling the air feels factoring in the humidity, could near or top 110 Friday through Sunday.
The exceptionally high humidity means temperatures may have a hard time cooling off at the evening, especially in urban areas, where temperatures may not drop below the low 80s while heat index values settle near 90.
The heat “will become a major threat to anyone exposed to the heat for an extended period,” the Weather Service warned. It is more likely to concern an excessive-heat warning Friday through the weekend, the most severe kind of heat alert.
This episode of extreme Heat is driven by a sturdy heat dome that has overtaken much of the Lower 48 and will peak in the Mid-Atlantic and Northeast on Friday and Saturday.
The heatwave is coming at the hottest time of the year in Washington, so even though it will be excessively heated, the intensity of the Heat may fall shy of daytime records. For instance, the forecast high of 100 on Saturday is unlikely to challenge the registration for the date of 106 degrees from 1930, which is also the highest temperature ever recorded in the metropolis for any day of the year.