As another long-term Windy Premium subscriber that's about to set up Home Assistant and disappointed to find that there is no API access included at all with Premium, I just want to add my +1 to this idea. Personally I'd prefer 2 or 3 fixed locations, but could make 1 work for my main needs. Very low usage limits (e.g. 50 calls/day) would be fine and this would probably offset some or all of my app usage at the moment, so it would probably net out to no impact to your backend :)