You could provide it a region or a specific location and it can give you the information for those coordinates. If you don't want to provide it location information 24/7, you should be able to deal with that "good enough" compromise.
This seems like a feature that the underlying OS should provide - if an app requests location but the user wants to provide rough region only, then the OS can simply provide, say, the center of the region instead of the true location; with a bonus that if you fly on a trip somewhere, then it can automatically supply the center of that region instead, again, without giving up the exact location.
I.e. permissions for privacy should not be treated as "grant or deny" but instead "grant true data or grant spoofed data".
It's trivial to specify location manually. Only partially related, but I get irrationally annoyed by websites repeatedly asking me to have my phone provide access to my location. In almost all cases, I'd much rather type in a 5 digit zip code and be done with it.
Hmmm but I think people using this feature will be extremely sensitive to it reporting it exactly for their current location. Forgetting to change your zip code and it silently telling you a light time off by five minutes could be a massive problem.
So just display a warning/confirmation prompt when the user chooses to use a fixed location rather than real-time location tracking. Or add the configured zip code to the data display.
This doesn’t seem like a safety critical feature that would warrant withholding the choice to opt out of third party location tracking
With how reliable I've seen location tracking anyway, I wouldn't bet my life on the device getting it right. I'd rather know that it is up to me, and be accustomed to updating accordingly.