fleas in winter

How cold must it be to end the “flea season?”  I live in the St. Louis area and currently it’s down in the low 30s upper 20s at night, but warms to 40s-50s during the day.  Last week it was in the 70s.  If it warms during the day, will the darn things continue to be active?  My pets have been plagued since July despite a visit from the bug man in August to spray inside and regular applications of Frontline.  From what I have read, I suspect I need to do some serious vacuuming and call the bug guy back.  I was hoping for a reprieve when the cold weather hit.

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