Philadelphia’s Climate: The Long View January 26 2009
JANUARY 1790 The average or medium temperature of this month was 44 degrees This is the mildest month of January on record. Fogs prevailed very much in the morning but a hot sun soon dispersed them and the mercury often ran up to 70 in the shade at mid day. Boys were often seen swimming in the Delaware and Schuylkill rivers. There were frequent showers as in April some of which were accompanied by thunder and lightning The uncommon mildness of the weather continued until the 7th of February.
Some interesting graphs at the link.
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