For many, Memorial Day marks the unofficial start of summer, but temperatures this weekend will barely reach balmy.
The National Weather Service frost advisories or freeze warnings extend through about 8 a.m. today, with the warning in place for counties north and east of Allegheny. Temperatures could dip into the mid-30s again tonight.
The weather service warned sensitive or unprotected plants could be damaged or killed by the cold.
An upper Midwest cold front has moved east but left a chill that is, for now, trapped here by high pressure over Canada, which is blocking any weather from moving in or out, said weather service meteorologist Brad Rehak.
For the record, this time last year, highs reached the 80s and 90s.
Dormont recreation director Kristin Hullihen was readying the borough's pool Friday afternoon, despite temperatures hovering in the upper 40s.
"Actually, I think the water is warmer than it is outside today," she said Friday, laughing.
Mayoral office spokeswoman Marissa Doyle said the city's spray parks don't usually open if the temperature is lower than 70 degrees. But grand openings celebrating the two latest additions in the Shadyside and East Hills neighborhoods will proceed as scheduled at 1 p.m. today.
Councilman Corey O'Connor took a run through the Shadyside spray park on a chilly Friday afternoon -- dressed in business casual.
City pools open June 14.
The lowest high temperature ever logged for May 23 was 52 degrees in 1877 -- until Friday, which set a new record with 51.
Temperatures should reach the mid-60s in Pittsburgh this afternoon under sunny skies. A high in the upper 60s is forecast for Sunday and the low 70s on Memorial Day, with plenty of sunshine. It should only get warmer from there.
"By Wednesday," Mr. Rehak said, "we're well into the 80s."