Polymarket weather markets for Tel Aviv settle on the official reading from LLBG. The settlement day runs midnight to midnight in Asia/Jerusalem, and buckets are one degree Celsius wide.
Check the market rules for the station, because the settlement station is the market's decision and can change. Remember the day boundary is Asia/Jerusalem: a market titled for one date can still be open while it is the previous day where you are.
Risk. Prediction markets carry risk and you can lose money. Nothing here is financial advice. Past results do not predict future results.