Is dry fasting safe? more specifically, no food or liquid for 25 hours straight? twice a year at most. thanks. p.s. consider praying outside for a few hours at a time on top of this, in 70 to 80f weather but with shade, would your answer change?

This would be entirely safe in most healthy people and at such moderate temperature. It would be wise to drink plenty of fluids in the hours before fasting starts, but even this is optional in healthy people without heart, kidney, or liver disease. But even healthy people could have serious problems if the temperature were, say, 90 and especially if over 100F.