That's always been a just-so story invented to justify insider trading. If weather predictors always bet on a weather prediction market, why would anyone else? They'd be guaranteed to lose money.

The meteorologist making the observation has the ability to sway the outcome. "Those automated observations were wrong, turns out the maximum temperature today was 61F not 60F." This already happens all the time. Whether insiders are doing this to win in prediction markets is up for debate.