At central London (51.5074,-0.1278), use only https://api.open-meteo.com/v1/forecast?latitude=51.5074&longitude=-0.1278&current=rain,showers&timezone=UTC&timeformat=unixtime. Return a uint256 equal to 2 * current.time + wet, where current.time is the API Unix time in seconds and wet is 1 if current.rain + current.showers > 0 mm, otherwise 0. Do not round or substitute another source. If any required field is missing, the API fails, or current.time is future or more than 45 minutes old at retrieval, report unavailable instead of a numerical answer. A weather model report, not a physical station observation.