October turning blue

October temperatures in Philadelphia are going to finish above normal, and the recent warmth may have something do with the fact that so many leaves are still green out there, but the month is about to take a blue turn.

By Thursday morning, temperatures are forecast to drop below 40 in Philadelphia for the first time in six months as a chill spreads across the East.

In Boston, the wind chills will be in the 30s for Game 1 of the World Series at Fenway. (At Citizens Bank Park, they will be near 40, not that it will matter.)

The official forecast lows for Philadelphia International Airport for the Thursday, Friday, and Saturday mornings are in the 30s, and the National Weather Service says a"widspread frost or freeze" is possible Friday and Saturday mornings outside the city.

No freezing readings are in the forecast for the city, itself, and it would be surprising if they were. When the low hit freezing on Oct. 31, 2011, after that freak snowfall, that broke an 18-year streak of freeze-less Octobers.

In the period of record dating to the 19th Century, on average Philadelphia has recorded its first official 32 reading around Nov. 8, with significant year-to-year and decade-to-decade variation.

For example, in the first decade of 21st Century, the average first date was Nov. 14, and Nov. 16 in the 1930s.

In the 1960s, the airport was reading 32 by Oct. 25 on average, and the freeze of Oct. 5, 1961, remains the earliest ever