Ball pythons move very slowly, so as long as you don't just walk off they aren't just going to crawl off and be gone. You do want it to be 75F or above to take them outside, and I prefer having low wind and a good amount of sun if it's below 80F. That way the ground will be nice and warm for them, and the air will be an acceptable range as well. I don't normally keep them out more than an hour, or two at most. Generally I have them out for about 30 minutes.