* Excessive heat watch on Saturday for heat indexes up to 110 *
Thursday marked the District’s fourth day in a row of 90-degree weather. But the heat we’ve experienced so far is tame compared with what’s on the way. This weekend, there is a strong chance that parts of the area will hit at least 100. Heat indexes, which take humidity into account, could reach 105 to 110.
According to the National Weather Service, the area’s HeatRisk, on a scale from 0 to 4, is set to escalate from Level 1 (minor) on Thursday to Level 4 (extreme) by Sunday. The HeatRisk scale takes into account how unusual and long-lasting the heat is, as well as the anticipated threats to human health.
If it does reach 100, it will be the first time since 2016. The nearly eight years without a 100-degree day in Washington is the longest stretch since the 1970s and the fifth-longest on record.
Because of the potential for heat indexes up to 110 on Saturday, the Weather Service has issued an excessive heat watch. Heat alerts will also probably be extended to Sunday. The watch in effect for Saturday is likely to be changed to a heat advisory or warning in the next 24 hours, according to the Weather Service.
The superhot days and too-warm nights will lead to increased risks to health over the coming days. A heat emergency plan in place for the city through Friday is likely to be extended through at least Sunday. Officials advise hydrating, taking frequent breaks if exercising or spending long periods outside, and finding air-conditioned places to cool off. Outdoor workers, older adults and the homeless are particularly vulnerable to extreme heat.
“Heat related illnesses increase significantly during extreme heat and high humidity events,” the Weather Service cautioned.
Here’s how hot it will get
After the last few days with highs in the low 90s, temperatures will start climbing Friday and peak this weekend.
On Friday, highs are mostly in the mid-90s. Some of our cooler areas north and west of the Beltway may reach only around 90. Humidity won’t be too bad yet.
Saturday has the look of the hottest day in many years, but it may hold that title only briefly. Temperatures in the afternoon should range from the mid-90s to around 100, with much of the local area in the upper 90s. Rising humidity levels (dew points near 70) make it feel like it’s about five to eight degrees hotter. An isolated cooling storm is possible, but don’t plan on it.
Sunday could be a degree or two hotter than Saturday for most locations. The forecast calls for 100 in the District and along much of the Interstate 95 corridor from Richmond to Philadelphia. Like Saturday, high humidity makes it feel more like 105 or so. There’s also a better chance of late-day storms, but probably after peak heating.
Low temperatures will also become increasingly uncomfortable through the weekend and will probably break records. On Sunday, the low in Washington may drop to only 80, which would be the warmest morning low since July 2019.
Records could fall
With predicted highs no higher than the mid-90s on Friday, most spots should fall just short of records. Dulles International Airport could come close, with a forecast of 96 and a record of 98.
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Better odds for records arrive Saturday, but they are all near or above 100, so many spots could fall just short again. The forecast at Dulles is 99, compared to a record of 99. In the District, the 99 in the forecast compares to 101 for a record.
Sunday seems to have the best shot to hit 100 and set some records. Washington, Dulles and Baltimore are all forecast to top records, with highs around the century mark.
A lengthy stretch of 90-degree days
The District has a streak of four days reaching at least 90 degrees, and that could keep going for a while, given the forecast. If the streak runs to at least eight days, it will be as long as any since 2020, when there was a 20-day streak, the second-longest on record.
There has already been a big turnaround in the number of 90-degree days this year. Before late last week, the District had posted just one, but now that count is up to seven, which is near normal for the date.
Little end in sight
Highs of 90-plus could continue until at least the middle of next week.
A passing dip in the jet stream may cool the area down closer to average (mid- to upper 80s) for a time thereafter. This could break the 90-degree streak, but the heat may reload after any brief cool-down.
Heading into July, the summer heat dome may reestablish itself over much of the country, keeping temperatures high in the Mid-Atlantic. The Weather Service is projecting high chances for above-normal temperatures over much of the country next month.
