When the sun sets today, one might appreciate the warmth of the rocket's red glare.

The creators of warm Christmases, cold Easters and the March 1993 blizzard have ordered up a nippy Fourth of July, with highs in the mid-70s and lows in the upper 50s.

"How about 76 ... That sounds very patriotic," National Weather Service meteorologist Lou Giordano said.

Patriotic, maybe, but not so great for pool parties.

Mr. Giordano said a low-pressure system stalled over the Great Lakes in recent days has spawned showers and clouds, depressing temperatures here. The normal July 4 high in Pittsburgh is 82 and the normal low is 61.

With the Great Lakes system finally breaking up and moving away, there will be more sunshine and dry conditions today, except for the possibility of an evening shower south of Interstate 70. Rain, not temperature, is the main foe of fireworks displays.

The low will hit about 6 a.m., and the high will come between 4 and 5 p.m. By 9:30 p.m. -- fireworks time in many communities, including Pittsburgh at the Point -- the mercury will have slid back to the mid-60s.

A stiff breeze could blow off the Allegheny, Monongahela and Ohio at times today, so boaters, picnickers and fireworks watchers along the rivers might want to dig out the red, white and blue windbreakers.

Mary Maslanik, chairman of Canonsburg's Fourth of July Committee, said she's telling people to "think sunny and dry thoughts." The borough's parade -- billed as the state's second-largest -- starts at 10 a.m. and fireworks begin at 9:45 p.m.

"It could be pouring rain and the street is still packed with people for the parade," Ms. Maslanik said. To reserve space along the parade route, she said, residents began putting out lawn and folding chairs a week ago.

The warmest Pittsburgh July 4 on record was in 1911, when the temperature topped out at 100 degrees. The coldest July 4 temperature was 46 degrees -- really bad for pool parties -- in 1968.

First Published: July 4, 2009, 4:00 a.m.