A rain under is a bet on the total points in a game staying under the posted line because of rain in the forecast. Rain makes the ball harder to throw and catch, so offenses run more, drives take longer and scoring drops. The market usually prices some of that in by lowering the total; the bet is that it does not price in enough. It is one of the oldest weather angles in NFL betting and one of the few that has held up in the data.
Updated Sept. 16, 2026.
Wind is the weather factor with the largest effect on scoring, because it ruins deep passing and field goals; rain is second. Both push offenses toward the run, which shortens the game and cuts explosive plays, and both raise the fumble and drop rates. The historical effect of steady rain on a game's combined score is a few points.
The question for a bettor is never whether rain lowers scoring, it is whether the total already moved enough. Books lower totals when a forecast is clear days in advance; the edge, when it exists, is in games where the forecast firms up late, where the rain is heavier than the early forecast, or where the public keeps betting overs on a game with two popular offenses.
This site tracks the angle in its trend ledger with a stated rule (forecast rain probability above a threshold at kickoff, outdoor stadium, and the total above a floor) and grades every qualifying game so the record is public. The angle is treated as an attribute of a game to price, not as a play to make blindly.
A game with a 47.5 total and a 70 percent chance of steady rain at kickoff at an outdoor stadium qualifies. If the total closes at 45.5 the market has taken two points; the angle bets that the true effect is larger. Over the sample the site has tracked, qualifying games have gone under at a rate above the break-even line, which is why it stays on the board.
The rain under is an angle, not a formula: a rule of the form 'outdoor game, precipitation probability at kickoff at or above X percent, total at or above Y', evaluated against the closing total, with the record kept over every qualifying game since the rule was set.
Yes, by a few points on average in steady rain, and more in heavy rain with wind. The effect comes mostly from fewer deep passes and more rushing, which shortens the game. Light rain has almost no measurable effect.
Less than it was, because books adjust totals for forecasts. The remaining edge is in late-firming forecasts and in games where public money on the over holds the total up. The site's angle ledger publishes the current record so the answer is a number, not a claim.
Wind is the stronger factor and the site tracks it separately; sustained wind above 15 mph is the usual threshold. Snow is rare and mixed: light snow has little effect, heavy snow behaves like heavy rain.
Category: Stats & Analytics. Part of the StickToTheModel NFL Encyclopedia.