There are microbes that work in cool weather/soil. In the spring often when the snow melts there will be snow mold. That mold is a fungus that thrives with little light and cold temps.

As DCHall stated, many microbes continue to function in cooler weather. Snow mold is one of them. However, the microbes that decompose organic fertilizers dramatically reduce their activity when soil temperatures drop below 50F. This occurred in the past few days in NE Illinois.

-Deerslayer

Thanks for the responses. Is there a place on the web to get soil temperatures for different parts of the country? I am too lazy to take my lawn's temperature, lol.

I remember reading/hearing that soil temp is closely related to AVERAGE night time low temps. Does anyone else recall anything about that? I'm not sure how that can make sense given the differences in moisture and shade.

Yes, you can get the soil moisture and temp from the link here. I selected the closest to Rutgers that I saw, but you may want to poke around.

Our soil temperatures at the 2" layer are spiking well above 50 during the day. That's going to flex downward this week as temperatures cool.

Here is a link that might be useful: SCAN Information Mahantango PA