D.C.-area forecast: Heat index near 100-105 tomorrow; storm chances return late tomorrow

Clear skies on Monday at the Hirshhorn Museum in D.C. (Joe Flood/Flickr)

Today’s daily digit

A somewhat subjective rating of the day’s weather, on a scale of 0 to 10.

6/10: Hot sun and low 90s, but not the worst humidity.

Express forecast

• Today: Mostly sunny, slightly hotter, but not too humid. Highs: Low 90s.
• Tonight: Mostly clear, becoming more humid. Lows: Low to mid-70s.
• Tomorrow: Mostly sunny, very hot and humid, evening storms? Highs: Mid- to upper 90s.

Forecast in detail

The heat edges slightly higher today before busting well into the 90s tomorrow, when the higher heat and humidity could push the heat index to around 100 to 105. Friday may not be quite as hot, with seasonably warm highs near 90 this weekend. As for rain, we shouldn’t see any today. But we could see an scattered storms tomorrow evening with a daily chance Friday through Sunday.

Today (Wednesday): High pressure dominates today, providing mostly sunny skies and keeping the humidity in check. The heat ramps higher as temperatures head for afternoon highs in the low 90s, but with humidity on the lower end of the moderate range (dew points in the low to mid-60s). Winds are light and variable in direction. Confidence: High

Tonight: Skies remain mostly clear as the humidity trends higher on a light wind from the south. Overnight lows fall back to the low to mid-70s. Confidence: High

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Tomorrow (Thursday): We’re mostly sunny again and trending even hotter with highs climbing to the mid- to upper 90s. With higher humidity (dew points near or past 70), we could see the heat index reach 100 to 105. By late afternoon and evening we run the chance of an isolated to scattered thunderstorm. Confidence: Medium-High

Tomorrow night: Isolated to scattered thunderstorms remain possible during the evening. Otherwise we’re partly cloudy and very muggy with lows in the 70s. Confidence: Medium-High

A look ahead

Friday through Sunday is a familiar summertime story with a stalled cold front nearby, which means partly sunny skies and a daily chance of showers and storms. Highs should be in the more seasonable upper 80s to low 90s each day with plenty of humidity (dew points near 70). Scattered storms could develop on any or all three days, mainly during the afternoon into evening, with each day carrying about a 40-50% chance seeing a storm at any given location. Confidence: Medium