I've used thermal to take deer during the day. I say take because I was using a collector's permit and it was out of season. I had no trouble at all using a 20mm IR Defense MK II.
It can be hard to tell the difference between bucks and does once the antlers have dropped but it is still doable if you look at body movements, and size. That and plus use of binoculars makes it really easy.
I used it mainly in the morning where temps are already in the high 70s and I still had no problems spotting or shooting the animal. One shot and DRT.