Summer at the fountain. (chasingmailboxes/Flickr)

* Excessive heat warning through 9 p.m. today, and excessive heat watch from 11 a.m. to 9 p.m. Sunday *

4:00 p.m. update: Heat index values have soared to 110 degrees this afternoon, the highest of the year so far. Here’s a map showing a range of heat indices from 105 to 115-plus around the region in the 3 p.m. hour:


Heat index values just before 4 p.m. around Washington. (National Weather Service)

Air temperatures have reached at least 97 degrees in the District, Baltimore and Dulles, making it the hottest day of 2019.

10:05 a.m. update: The low this morning of 81 degrees in Washington was just one degree below the record warm low temperature for the date of 82 (from 2015). The 10 a.m. temperature of 91 and heat index of 100 is running ahead of yesterday’s temperature of 89 and heat index of 96 at the same time. We have a good chance to hit 100 today for the first time since 2016.

Here’s our national story on the heat wave: Stifling heat to rule the weekend for two-thirds of the Lower 48 states, with records in jeopardy

From 5 a.m.

TODAY’S DAILY DIGIT

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

1/10: If anything, it might be less pleasant than Friday. But it’s a weekend and not the worst day ever to spend in the water, as long as you stay hydrated (and sunscreen-covered).

EXPRESS FORECAST

Today: Mostly sunny. Hazy and humid. Highs: 96 to 101.

Tonight: Mostly clear, remaining unpleasant. Lows: Mid-70s to low 80s.

Tomorrow: Partly to mostly sunny. PM storms? Highs: Mid-90s to around 100.

View the weather at Washington Post headquarters.

FORECAST IN DETAIL

It’s the second day of this run of extreme heat but the 10th consecutive day of 90 degrees or greater. While there is finally a break on the horizon, we have to go through what is likely to be the worst we’ve seen yet. Today’s a good one to stay indoors in a cool place if you can, or at least limit your time outside while downing tons of water. Even at night, the relief will be limited. Truly a time to take it easy, check in on those who may need assistance, and know the signs of heat illness.

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Today (Saturday): Like yesterday, we’re off to the races as soon as the sun is up. Heck, many places start in the 80s even before it’s up. Highs head mostly for the upper 90s to around 100. We should end up a degree or two hotter than Friday in most spots. With dew points in the 70s, humidity is very high, and heat index values rise to a peak range of 105 to 115 this afternoon. There’s a small chance of a pop-up storm, but high pressure aloft should work against storm development. Confidence: Medium-High

Tonight: It stays torrid through the evening and into the night. We’re still dealing with temperatures near and above 90 deep into the overnight, with heat indexes near and above 100 until about midnight in the city or right on the water. Lows settle only to a range of mid-70s to low 80s, which is near record territory. Confidence: Medium-High

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Tomorrow (Sunday): Given the high launching point of toasty lows, this seems to be another day destined for the near 100 zone. It’s often the day before the arrival of a front that ends up the hottest of the bunch, so we’ll have to see if that comes together and temperatures end up higher in close. High humidity leads to another round of heat indexes in the 105-to-115 range. There’s a somewhat better chance of storms than in recent days but still far from a guarantee. Confidence: Medium-High

Tomorrow night: We may be dealing with some evening showers and storms. If so, they’re tapering off into the night. If no storms, another night with lows in the mid-70s to low 80s is likely. If we do get the storms, more like 70s for everyone. Still way too humid. Confidence: Medium-High

A LOOK AHEAD

We’re still trying to time the front out on when it passes. For now, it’s back to later Monday, which should mean temperatures rise to around or above 90 for a 12th straight day. Odds are good that clouds will be rather numerous and showers or storms develop in the afternoon. Confidence: Medium

Getting to Tuesday, the front is headed south, but a wave of low pressure may move along it, keeping us in the clouds and occasional rain. Something tells me the temperatures in the 80s will keep the complaints about the rain to a minimum. We’ll have earned a break by then. Confidence: Medium