Boiling enough water takes a lot of time, work, and fire.
Solar “ovens/stills” will pasteurize water. Heck, your car will work if you live in a sunny and warmer climate. Boiling for ten minutes or warming to 140 for ~6-8 hours will acomplish the same thing. I have a few solar shower bags stashed for hygene and pateurizing. Given rain, a fresh water stream and sunlight you can do a lot.