Dropped down to 18 degrees at my place last night. How do you like that, you ticks and chiggers?!!
Far fewer ticks is one of the best things about winter, and true, the cold keeps them mostly inactive, but unfortunately I don't think it really ever gets cold enough here to actually
kill a lot of them.
In lab conditions, ticks start to die at temperatures less than 14°F, but in the wild they have been shown to overwinter at temperatures below -2°F, by using leaf litter and snow as insulation. They can also generate a cryoprotectant when they're in diapause (hibernation). Some ticks also survive by remaining attached to animals.
DCNR's Bureau of Forestry explains how the recent frigid, winter weather across Pennsylvania can impact the tick population.
www.dcnr.pa.gov
In practice it would probably take three or four days with temperatures at -10°F or colder to really put a big dent in tick populations. Or alternatively, they can be killed by periods of warm weather that trick them into venturing out, followed by a sudden and severe cold snap.