Today (Sunday): Our several-day heat wave begins today as afternoon temperatures rise through the low and mid-90s under mostly sunny skies. The humidity isn’t horrible, but it does climb toward the moderate range with dew points in the low to mid-60s. That means afternoon heat indexes reaching the mid- and upper 90s. Winds are light from the west around 5-10 mph. Confidence: High
Tonight: The heat sticks around with lows only dropping to near 70 to the mid-70s under mostly clear skies. It’s slightly more humid, too. Confidence: High
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Labor Day (Monday): It’s shaping up to be one of our hottest Labor Days on record with mostly sunny skies and afternoon highs in the upper 90s. Humidity remains in the moderate range, likely pushing the afternoon heat index to near 100 or into the low 100s. Just a slight chance of a late-day thunderstorm. We could break records at Reagan National Airport (96 set in 2019), Dulles International Airport (95 set in 1985) and Baltimore-Washington International Marshall Airport (96 set in 2019). Confidence: Medium-High
Tomorrow night: Mostly clear and warm conditions continue. We could challenge record-warm lows overnight with temperatures only falling back to the mid-70s. Confidence: Medium-High
High pressure continues to camp out overhead through Tuesday and Wednesday, both of which are likely to see record-challenging heat with mostly sunny skies. Daytime highs should reach around 95 to 100, with heat indexes again topping out near 100 or in the low 100s. Still just a slight chance of a late-day thunderstorm both days. Tuesday night lows stall in the 70s again. Confidence: Medium
Temperatures may again rise well into the 90s on Thursday, with highs probably closer to 90 on Friday, with the chance of a shower or storm starting to increase. Confidence: Low-Medium
Read More: D.C.-area forecast: Serious September heat wave starts today, then sizzles through midweek
