Heat wave expected to last a week or more
A second wave of summer heat is bearing down on Baltimore — one that could last a week or more.

A high of 90 degrees Wednesday at Baltimore-Washington International Thurgood Marshall Airport marked the start of what could be at least a seven-day stretch with highs in the 90s or above. The National Weather Service is predicting temperatures in the upper 90s through at least Tuesday, but other forecasters expect the heat to linger much longer.

That has health officials ready to open cooling centers and Baltimore Gas and Electric Co. expecting a surge in power use.

The heat wave could be the longest in a year, but would have to last for weeks to set a record. Earlier this month, temperatures peaked at 100 during a five-day stretch above 90 degrees.

The weather service issued a heat advisory for Central and Southern Maryland and the Eastern Shore from 11 a.m. to 8 p.m. Friday, with a high of 100 and heat index of 105 expected.

Maryland health officials activated a statewide heat plan for Friday, urging residents to seek relief from the heat and be wary of heatstroke and heat exhaustion. The plan is in effect for Central Maryland and the Eastern Shore through Sunday.

Baltimore health officials said they plan to open cooling centers Friday through Sunday; Anne Arundel County is opening cooling centers Friday through Monday.

BGE was not expecting electricity use to reach peak levels Friday but is focusing on key equipment and planning for added staffing as needed over the next several days, spokeswoman Rachael Lighty said. On a typical summer day, BGE customers use about 5,500 megawatts of electricity; a record 7,236 megawatts was used July 21 last summer.

The longest stretch of highs above 90 at BWI is 25 days, set in July and August 1995. A nine-day stretch in the 90s would rank in the top-40 longest spans of 90-degree weather in Baltimore, according to weather service data.

A stretch last summer neared record lengths: Highs were in the 90s and above for 17 days straight through Aug. 2. There were a handful of heat stretches lasting five days or fewer.

In 2010, highs were in the 90s and above for 11 days, ending July 25.

The weather service forecast extends only six days, but AccuWeather, which recently debuted a 25-day forecast, is calling for highs in the 90s through July 9. That would be a stretch of 13 days with highs above 90 degrees.

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Forecast highs

Friday: 100

Saturday: 98

Sunday: 99

Monday: 98

Tuesday: 95

Source: National Weather Service