An osprey family watches over the Capitol from their perches on the Potomac River, July 18 (Carol Jean Stalun/Flickr)

* Excessive heat warning 11 a.m. through 9 p.m. today | Code orange air quality alert today | Excessive heat watch Saturday and Sunday *

6:55 a.m. update — Today’s heat advisory upgraded to excessive heat warning

The National Weather Service upgraded today’s heat advisory to an excessive heat warning between 11 a.m. and 9 p.m.

“An Excessive Heat Warning means that a prolonged period of dangerously high temperatures will occur,” the Weather Service service writes. “The combination of extreme temperatures and high humidity will create a dangerous situation in which heat illnesses are expected.”

From 5 a.m.

TODAY’S DAILY DIGIT

1/10: It’s almost as bad as D.C. summer gets, with 110-degree heat index values possible. One point is held in reserve, as it might get worse this weekend.

EXPRESS FORECAST

Today: Mostly sunny, hot and sultry. Highs: mid-90s to about 100.

Tonight: Partly cloudy, still steamy. Lows: mid-70s to low 80s.

Saturday: Dangerous, oppressive heat. Highs: near 100 to low 100s.

Sunday: Afternoon storms possible. Highs: mid-90s to about 100.

View the current weather at The Washington Post.

FORECAST IN DETAIL

As the heat gets serious today and through this weekend, please remember to find as much air conditioning as possible so your body doesn’t dangerously overheat. The air will feel close and oppressive, because our bodies can’t naturally and easily cool themselves. Keep water handy as well!

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Today (Friday): Temperatures may top out in the upper 90s to about 100 degrees. When adding in oppressive humidity levels (dew points mid-70s or higher) on top of the hot temperatures alone, heat index values around 110 degrees are possible. That’s serious heat stress on our bodies. Air quality is also poor. With high pressure building in overhead, storm odds are quite low to nil. Confidence: High

Tonight: Much of the region may still feel like an oven, even after dark. We only slowly get toward predawn low temperatures in the mid-70s to low 80s. A heat wave turns extra dangerous when low temperatures do not get below 80 degrees, so we are concerned. Find air conditioning if at all possible. Confidence: High

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(The Washington Post)

Tomorrow (Saturday): The core of the heat “dome” of oppressive, hot high pressure moves into our region. We’re sunny and sweating for sure, with temperatures near 100 to low 100s for the region. Heat index values could approach 115 degrees. This is dangerous heat, because of the added oppressiveness of the humidity (dew points well into the 70s). Our bodies do not have the ability to self-cool through normal sweating. It’s just too hot and muggy. Be careful. An isolated storm or two may pop up in the extreme heat. Confidence: High

Tomorrow night: Still oven-like for much of the night. Upper 70s to low 80s are the coolest we may be able to manage for an hour around or just before sunrise. Keep that air conditioning humming. Confidence: Medium

A LOOK AHEAD

Sunday: It’s continued steamy and oppressive, with very high humidity (dew point at least 75 degrees) accompanying temperatures in the mid-90s to about 100 degrees. We may see a few late-afternoon showers or storms, so keep your fingers crossed for this relief. Rain chances remain low. A few areas could see strong storms with damaging winds and flooding downpours. Confidence: Medium

Sunday night: Some showers and storms have a 50 percent chance of moving in. If you’re lucky enough to see rain, you could cool quickly and effectively, perhaps within a few degrees of overnight low temperatures in the mid- to upper 70s. Confidence: Medium

Heat may reduce as a cold front passes Monday. By Tuesday it hopefully moves through the area. Clouds may bubble up for much of each day, along with possible showers and storms. Tote around a small umbrella to play it safe. High temperatures mercifully top in the 80s both days, upper on Monday and low to mid for Tuesday. We’ll keep an eye on the slight potential for strong storms as we get closer. Confidence: Medium