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THURSDAY OCTOBER 5 - DATE OF EARLIEST FROST
The average date of the earliest 32oF or lower temperature in the fall is about
the first of November around here - earlier than that in outlying areas.
in Philadelphia, the earliest freezing temperature occurred on this date back in 1961,
when the mercury dipped to 31oF. In Wilmington, the temperature's actually fallen to
freezing as early as September 27, and below freezing as early as October 1. So we've
certainly reached the time of year when it's at least possible to see freezing
temperatures, even in city areas.
Of course, the first freezing temperature can also arrive fairly late in the fall.
In fact, in two years, 1931 and 1939, October and November were officially frost-free,
with the first 32oF temperature not coming until early December.
Keep in mind that official temperature readings are taken a few feet above the surface.
But right at ground level, the temperature is usually lower at night. So you can get
frost on your grass or on your car even on nights when the "official" temperature
doesn't drop to 32oF or below.