Temps will be better the next three days after tomorrow. Put it off if you can. Go ahead if that's the only time you can. I've made a bunch of splits already, even some yesterday between the rain showers.
If it is cool, low wind is really important and the job needs to be done while the day still has some heat in it. Not a job for after work on a fifties day. Then it gets colder and the bees don't have time to get things organized. The warmer it is, the less damage is done. Fifties with low wind until early afternoon is good.
It kinda depends on how you plan to go about it. If you are searching frame by frame to find the queen upper 50s would be less likely to chill brood. If you are just sorting things quickly and not queen looking it can be a bit cooler.
A forum community dedicated to beekeeping, bee owners and enthusiasts. Come join the discussion about breeding, honey production, health, behavior, hives, housing, adopting, care, classifieds, and more!