Public health authorities urged Maryland residents to take precautions against heat exposure this week as temperatures head back into the mid-90s, with plenty of humidity to add a sticky factor to the misery index.
High temperatures Wednesday and Thursday are expected to reach 96 and 98 degrees, with high humidity making it harder for the body to cool itself by evaporating sweat from the skin.
"Extreme heat can be deadly," said state Secretary of Health Dr. Joshua M. Sharfstein. "Everyone should review the warning signs of danger."
Last week's heat wave also sent temperatures at BWI-Marshall Airport to record readings in the upper 90s and contributed to the deaths of two Marylanders, the first heat-related fatalities of the year, according to the Department of Health and Mental Hygiene.
Both victims were residents aged 65 or more, and both had underlying medical conditions. One was a Cecil County man, the other an Anne Arundel County woman. No further details were released.
In 2010 — which saw the hottest summer on record for Baltimore — there were 32 confirmed heat-related deaths in Maryland, state officials said. In 2009 there were six, in 2008 there were 17, and in 2007 there were 21.
Gov. Martin O'Malley joined the call for residents to look after each other this week. "We need to remember to check on our families, friends and neighbors and especially those who are most vulnerable," he said.
Baltimore County school officials announced students there would be sent home two hours early on Wednesday and Thursday because of the heat. City schools were also sending students home early on Tuesday, operating on a half-day schedule and canceling after school activities. And in Anne Arundel County, a partial power outage affecting air conditioning was causing Waugh Chapel Elementary School to close at 11 a.m. Wednesday.
Temperatures at BWI on Tuesday topped out at 90 degrees, the fifth 90-plus day of the year.
But there is hotter air on the way Wednesday as high pressure and sunshine combine with southwest winds in a sure-fire recipe for hot weather in the Chesapeake region.
"We have a high-pressure system sitting over us, and that's going to clear out some of the sky cover we had [Tuesday]," said meteorologist Carrie Suffern at the National Weather Service's regional forecast office in Sterling, Va.
Southwest winds will bring in Gulf Coast humidity, and winds "down-sloping" off the Appalachians will compress and heat it up to at least 96 on Wednesday.
"Thursday is looking like the warmest, with highs for the Baltimore area of 98," Suffern said. "That's going to mean heat indices over 100 degrees."
The weather service issued Heat Advisories from Frederick eastward to Cecil County, and south to the Potomac, effective from noon through 8 p.m. Wednesday. The advisories call for Heat Index values as high as 105 degrees at BWI-Marshall Airport.
Temperatures Wednesday could reach 97 degrees in downtown Baltimore. The city's Health Department issued another Code Red Heat Alert for the day, opening 11 cooling shelters across the city to help residents without air conditioning find a place to chill out and rehydrate.
And the Maryland Department of the Environment posted another Code Orange Air Quality Alert, warning that airborne pollutants will rise to levels considered unhealthy for sensitive groups, including children, the elderly, and people with respiratory illnesses.
The record temperature for Baltimore on June 8 is 97 degrees, set 12 years ago, in 1999. The record high for June 9 is 98 degrees, reached most recently on that date in 1933.
An approaching cold front should bring a 30 percent chance for some thunderstorms late Thursday, and bring temperatures back into the near-normal mid-80s by the weekend.
This week's heat wave is the second of the season. Highs of 98, 97 and 98 degrees on May 30, 31 and June 1 all set or matched record highs for Baltimore on those dates. That hot spell, too, came with Heat Advisories, air pollution alerts and Code Red declarations in the city.
Even so, the National Weather Service continues to see equal chances for this summer's temperatures to end up below-average, average or above-average.
"There are no major climate signals stating it will be an above-normal summer, temperature-wise," Suffern said.
How to deal with the heat: http://bsun.md/kWxX0y
http://twitter.com/froylance