Hot. Hotter. Hottest. How's your AC?

Today marks the eighth straight day of 90-degree-plus weather at BWI-Marshall, the fourteenth such day this month and the thirty-sixth so far this year. So how's your AC holding up?

You'd better hope it's in fine shape, because the next few days will be killers. Perhaps literally.

UPDATE 1:00 p.m. Thursday: The Baltimore City Department of Health has declared Code Red Heat Alerts for Friday and Saturday. Cooling centers will be opened across the city. Call 311 for times and locations. At 2 p.m., the NWS issued Heat Advisories for the region from noon to 9 p.m. Friday.

Forecasters out at the NWS forecast office in Sterling are predicting a high today (Thursday) of 93 degrees at BWI-Marshall Airport, and that was the reading at 3:45 p.m. For reference, it was 91 at Tefe, in the Brazilian Amazon. It may not feel as awful here; the air is a bit less humid. But it goes downhill from here.

Friday is expected to reach a high of 96 degrees at the airport as we come under the influence of that Bermuda High in the western Atlantic Ocean. Humidities will rise, pushing heat index readings into the 95 to 105-degree range. There's only a slight chance for a cooling overnight shower before Saturday.

And Saturday will be the worst day of the week (see map). High temperatures at BWI are forecast to push into triple digits for the sixth time this summer, with even less cloud cover for shade than on Friday. Humidities will be high, driving heat index readings into the 100 to 110-degree range. You had your AC system serviced this spring, right? Good.

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Watch for heat advisories, Code Red advisories and such. You know the drill by now. Just stay inside or go where it's cool. The jogging, the roofing, the post-hole digging can wait.

Eric the Red, a professional meteorologist from Baltimore who kept us ahead of the bad news during last winter's snowstorms, says it will be a memorable day.

"I am beginning to think Saturday might end up being one of the worst - if not THE worst - day of the summer. Temps will likely exceed 100 degrees yet again, but this time 'round our dew point may very well be in the lower 70s [oppressively humid]."

Eric sent along the temperature forecast map above. "This is NOT the max. temp. forecast, but rather a snapshot," he said. "I suspect the highest readings will be a bit above what the graphic shows. Ouch."

There's more from Eric below. Click on "Continue reading..."

While we're on the subject, BGE today issued (and later recalled) a press release warning customers with central AC that the electric bills they receive in the next few weeks will reflect the extra energy used during the persistent heat of recent weeks. Some bills may double, the utility said.

The torture continues.

Eric the Red continues:

"Impressive numbers are rolling in for Saturday's heat potential.

"Quick Meteo 101: You may recall me talking during the winter about temperatures aloft... more specifically, at ~ 5,000 ft (850 mb)... and how you need to be below freezing at that level to get snow. Well, during the summer, you can use the temperature forecast at that level to also get a pretty good idea of what your heating potential is at the surface. (There's a bit more to it than this... involving dry versus moist adiabatic lapse rates, surface pressure, convective temperatures, mixing ratios, and compressional heating... but I'm assuming you don't really care for that level of detail. (Or do you?!) )

"Anyway... here are the details:

"For Friday, the models forecast the temperature at ~ 5,000 ft (850 mb) to hit 23°C/73°F. Mix that air down to the surface, sans clouds, and you have a max temp of 99-101°F Hmmm.

"For Saturday, the models forecast the temperature at ~ 5,000 ft (850 mb) to hit 25°C/77°F. Mix that air down to the surface, sans clouds, and you have a max temp of 103-106°F Double Hmmm.

"The WRF [a forecast model] brings showers into the area on Saturday, which put a lid on the extreme (100+) heat. But the GFS [another forecast model] is all about 48 hours of humid, hellish, pure sun-shiney fun! Considering we'll be at a baseball game... I'll go with the GFS. Another scoorcher. Upper 90s tomorrow, 100-degree heat a good bet on Saturday (assuming clouds/showers don't enter the picture). Enjoy! - E"

Hot. Hotter. Hottest. How's your AC?

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