Across every outdoor NFL game since 2006, as the Weather Football Index rises the game transforms in a consistent, physical way: the passing game collapses, offenses lean on the run, and kicking accuracy falls off — especially from distance. That's the mechanism behind lower scoring and the unders. Each bar is grouped by WFI band.

The takeaway: bad weather is a run-funnel and a kicking tax. It compresses the passing game (fewer attempts, lower completion %, less on deep balls) and shaves points off field goals — which is exactly why totals come in under the market as the index climbs.