Dry conditions slow down the microherd to almost nothing (biological processes require water, but your irrigation does wick up, plus any dew you get helps), but they don't usually kill it off. Bacteria are happy to spore up and wait for wetter weather. Your arthropods in the top layers are pretty sturdy when it comes to wet/dry cycles (or they would have died out hundreds of millions of years ago).

Hot, wet weather does accelerate organic decay, such as in a rainforest. Decay at under 50 degrees is fairly slow, as it drops through the forties toward freezing it really slows down. It never quite stops, however--temperature spikes usually take the surface soil temperature over freezing many times a winter, even if it's frost-locked a bit deeper.

I wouldn't worry about it too much, except that I wouldn't apply organics when temperatures are in the fifties and dropping. They'll hang around until spring and runoff becomes a real danger with frozen ground.