Temperatures crowded 100 degrees and kept Central Maryland in the steamer Wednesday. The summerlike swelter closed classrooms, opened city pools and hydrants, and sent residents in search of whatever air-conditioned spaces they could find.
The mercury at BWI Marshall Airport reached 99 degrees at 2:38 p.m., beating the 12-year-old record of 97 degrees for the date. It was the fourth 90-plus record high in 10 days. High humidity drove the Heat Index — a measure of how hard it is for the body to cool itself — to a suffocating 106 degrees.
Frederick Airport reported a high temperature Wednesday of 102 degrees.
"It was pretty warm out there," said Carrie Suffern a meteorologist at the National Weather Service forecast office in Sterling, Va.
The outlook for Thursday isn't much different. The weather service predicts a near-record afternoon high of 97 degrees, with more stifling humidity and poor air quality. Friday's readings could also reach 90 degrees at the airport. But a passing cold front and accompanying showers should begin to lower temperatures into the 80s by the weekend, forecasters said.
The forecast for Thursday was enough to prompt Baltimore County schools to announce another two-hour early dismissal.
City school officials, who also dismissed classes early Wednesday, will again have a half-day schedule for Thursday. Amid the spring heat wave, Mayor Stephanie Rawlings-Blake ordered that two public swimming pools be opened to "provide an opportunity for young people and families to stay cool and safe."
Pools at Druid Hill and Patterson parks were to open from 3 p.m. to 8 p.m. Wednesday and Thursday. The pools are not scheduled to open regularly on weekdays until June 25.
A few city residents opened fire hydrants illegally Wednesday in their quest to cool off. The Department of Public Works, which received reports of five open hydrants between noon and 3 p.m., said the opening of high-pressure hydrants endangers children and lowers water pressure, which could hamper firefighting.
Baltimore health officials said hospitals treated eight people Tuesday for heat-related illnesses. But Brian M. Schleter, a spokesman for the city Health Department, said, "We believe the volume of heat-related illness is actually much greater."
Two of the 11 hospitals polled had not yet reported in, he said, and diagnosis codes do not always reflect the role of high temperatures.
"For example," he said, "a stroke or heart attack patient isn't likely to be coded as heat-related, even though heat may be a contributing factor."
This week, the Maryland Department of Health and Mental Hygiene reported two heat-related deaths during last week's three-day heat wave.
Residents without air conditioning in their homes, or with no homes to go to, were urged to seek shelter and chilled water in one of the 11 cooling centers opened during the Code Red Heat Alert declared this week.
The city did not have a count of residents using the shelters this week. During Code Red emergencies May 31 and June 1, the busiest, the Sandtown-Winchester Senior Center in Southwest Baltimore, recorded 372 visits over two days.
Wednesday was the sixth day this season with daytime highs in the 90s. Last year the airport counted 59 days with highs of 90 degrees or more, a record for Baltimore. Last summer was the hottest on record for the city.
Summer won't officially begin for 13 more days.
In the meantime, forecasters have posted another Heat Advisory for Thursday, effective from noon to 8 p.m., with highs in the upper 90s and high humidity pushing the Heat Index as high as 105 degrees. The Code Red Heat Alert in Baltimore remains in effect through Thursday.
As the heat combined with sunlight and engine exhaust to boost surface ozone levels, Code Orange Air Quality Alerts were in place Wednesday from New York to Washington, across much of the Midwest and south to Georgia. The alerts were extended through Thursday in Maryland east of the mountains, including the Eastern Shore.
The late-spring heat has come with hit-or-miss showers and thunderstorms. Barely a quarter-inch of rain has fallen at BWI since May 20.
Heat and humidity have spurred demand for electrical power to run fans and air conditioners.
BGE spokeswoman Linda Foy said the highest consumption for the month so far was June 1, when customers used 6,651 megawatts. That was short of last year's June peak of 6,675 megawatts and well below the all-time summer peak of 7,198 megawatts on Aug. 3, 2006.
"At this time, it doesn't look like we are going to set a new all-time peak," Foy said. But "we certainly would encourage our customers to conserve energy whenever they can."