IDK of anything more backing the derivatives than the funds of the bettors, and the guy with the hot-air gun heating up the official thermometer at the Paris airport... [0]

[0] https://www.businessinsider.com/polymarket-paris-weather-bet...

Bets on regional weather emerged as a way for farmers (especially citrus growers in marginal non-tropical zones) to hedge against weather-related crop loss.

If you're long Florida grapefruit futures, hedging against an early freeze is an economic trade on the future value of a real thing.

Futures contracts exist as insurance contracts. The fact that people can trade them as gambling items doesn't mean they exist as gambling.

Almost anything can be gambling if you make it gambling. Effectively all the assets in the securities world that can be bought and sold as derivatives exist to facilitate and existing industry by offsetting risk.