The official beginning of summer is 7:09 p.m. Wednesday, but it will feel very much like summer starting today.
Temperatures are expected to climb into the low 90s today, Wednesday and Thursday.
Today and tomorrow will be mostly sunny with a high of 93. Thursday will see a high of 91 with a chance of thunderstorms, according to the National Weather Service.
Pollution levels in Liberty and Clairton will be high enough to irritate some people tomorrow, forecasters warned.
The NWS has issued a code orange warning for the area, meaning that young children, senior citizens and people with breathing or heart problems might find it more difficult than usual to breathe. People who are susceptible to the pollution should avoid strenuous activity and outdoor exercise, forecasters said.
The city of Pittsburgh has increased the number of senior centers that are staying open late to give residents relief from the heat.
The Greenfield, Mount Washington and Sheridan centers will stay open until 7 p.m., three hours later than usual, today through Thursday, officials said today.
The city previously announced that the Homewood center would stay open until 7 p.m. today through Thursday.
The centers, which open at 8 a.m., are for residents 60 and older.
Dewpoints in the next few days are expected in the mid 60s, which could be a bright side.
"There won't be enough humidity to make heat indexes that are much higher than the actual temperature," said Tom Green, meteorologist at the National Weather Service in Moon.
The worst of the heat will be over by Thursday night, according to the weather service.
"We'll have a chance of rain coming in Thursday afternoon," Mr. Green said. "That's what's probably going to end up bringing temperatures back down."
EPA excessive heat guidelines warn not to leave children or pets in the car on a hot day. They also advise checking on elderly or sick people, who could have trouble dealing with the heat.
Peter Sullivan: firstname.lastname@example.org or 412-263-1939. First Published June 19, 2012 11:45 AM