The National Weather Service forecasted temperatures approaching record highs in the mid-90s today and Thursday, before cooling down into the low 80s this weekend with the possibly of rain.
"Temperatures will be close to record highs, but it's unlikely they will pass them," said Kevin Fitzgerald of the National Weather Service.
Record temperatures in Williamsport are 98 for today and 99 for Thursday; record temperatures in Harrisburg are 96 for today and 97 for Thursday.
Humidity levels will also be higher, peaking on Thursday at approximately 65 percent, said Fitzgerald.
Rain is unlikely for today, but there is a higher chance for precipitation Thursday afternoon into early Friday as a cold front moves in overnight, said Fitzgerald.
Forecasted high temperatures on Friday are in the low 80s, and are predicted to drop to the low 70s for Saturday, when it's expected to rain.
Heat watch
The hot temperatures and high humidity have caused the National Weather Service to issue an excessive heat watch from Wednesday afternoon through Thursday evening for much of southeastern Pennsylvania, northern Delaware and the western part of central New Jersey.
It might seem early in the summer season for such oppressively warm weather but Greg Heavener of the National Weather Service in Mount Holly, N.J. said the heat is not unseasonable for this time of year. The first heat wave of 2010 was June 1 to 5 and the first heat wave of 2009 was April 27 to 29, he said.
The weather service defines a heat wave as three consecutive days of temperatures reaching 90 degrees or higher.
That is not expected to happen this week, as temperatures are only expected to reach into the 90s on Wednesday and Thursday, Heavener said.
Heavener urged people to use common sense: Stay in air-conditioning whenever possible, limit strenuous exercise to early morning or evening, wear light weight and loose fitting clothing and drink plenty of water.
Temperatures should become more comfortable on Friday, reaching the high 80s, and continue to fall over the weekend to about 80 degrees on Sunday and Monday, according to the weather service.