How wind speed causes points scoring to subside

How wind speed causes points scoring to subside

By Mark Taylor Sep 15, 2014

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The impact of weather on scoring is often neglected by NFL bettors when betting on the total number of points scored in a game. This article highlights how wind speed causes points scoring to subside in NFL, creating an opportunity to gain a potential NFL betting edge.

For those who do not wish to take sides when betting on an NFL game, the obvious alternative is the total number of points scored in the game, including overtime.

The NFL has seen a steady increase in the total number of points that bettors can expect to see scored in a game since its reformation in 2002. With the exception of minor peaks in 2002 and 2004, totals averaged below 42 points per game until 2007, after which an increase in passing, along with various offense friendly rule changes, enabled totals to trend upwards.

Since 2010, totals have averaged 45.5 points per game (ppg), while the opening week of 2014 posted a decade high of 46.7 ppg.

Unsurprisingly, even at these historical highs, the trend has not gone unnoticed by the oddsmakers and although overs were more plentiful than unders since 2013, they still only had a winning strike rate of 51.3%.

Team based factors play an obvious role in determining match totals. Passing the ball has the potential for large gains, quick scores and often preserves the clock, whereas a side committed to running the football may be expected to score more slowly, while keeping the clock running.

Matchups are also important, especially as a side can rarely be elite on both sides of the ball. A side which has an excellent offense may also have a below par defense, creating the conditions for a high scoring match.

The impact of weather on NFL scoring rates

However, an area often neglected by bettors when considering match totals is the impact of weather on scoring rates. Dome sides are immune, but excessive wind speeds can be a considerable hindrance to both the passing and kicking game.

A comparison between the average totals recorded for games played indoors and games that were open to the elements appear to confirm the differences. Over the last decade matches played under a dome averaged a shade over 46 ppg compared to around 42.5 for those played outdoors.

However, as with total markets as a whole, the tendency for a dome game to have higher total scoring has also been largely accounted for in the quoted lines.

A comparison between NFL games played under a Dome and Outdoors (2003-2013)

Dome/Retractable Roof

Outdoors

Average Points per Game

46.2

42.4

Average Under/Overs Quote

44.6

41.7

The sample of dome games is smaller and the percentage of such games that went over the total quote since 2003 allows for a small profit, especially at odds of 1.950 offered at Pinnacle Sports. But these results may just be a random fluctuation and not indicative of future expectations, especially with the oddsmakers at liberty to edge their totals higher and sample sizes are relatively small.

Actual game totals for outdoor NFL matches also average slightly more than the average bookmaker game totals, possibly as a result of the skewing effect – 106 points were shared by the Bengals and the Browns in 2004. But individually, outdoor overs have a strike rate of just 49.3%.

In short, total quotes for indoor games slightly under estimate the amount of games that go over the total, while outdoor contests appear to under estimate the tendency for totals to go under mark, but not to a significant degree in either case.

The additional factors which may contribute to game totals is limited in domed games, but as already mentioned, weather can potentially intervene outdoors. So there may be a way to identify untapped value within this larger sample of outdoor matches.

How wind speed relates to points Totals in the NFL

Game day weather is available to bettors and the information ranges from temperature, humidity, as well as wind speed and direction.

In the plot above, I’ve shown the average points per game for outdoor games played in the NFL since 2003 as the strength of the wind increases.

Wind would appear to be of little consequence to a game’s rate of scoring until it reaches speeds of 15 mph and above. The aggregate totals remain fairly consistent above 40 ppg until then, but begin to show a definite and accelerated downward trend, especially at speeds of 20 mph and above.

The most extreme wind conditions for the ten-year data came in Week 17 at Buffalo’s Ralph Wilson Stadium for the visit of the Patriots in 2008. Although not the only factor conducive to a low scoring game on the night, the average wind speed was 32 mph, gusting to 55 mph.

82 rushing attempts in total were made by the two teams and only 33 passing plays, yielding 13 points in total. The over/under line for the game was set at 34.5 in anticipation of a low scoring game, but still not low enough to prevent a successful under bet.

This single game mirrors a more general trend, that is especially noteworthy when average wind speed attains 20 mph or greater. In the 50 or so such games, average totals were set on the low side at 38.5, but actual match totals averaged even lower at 35.3 and consequently under bets were successful in 64.6% of games.

Historically, wind speed would appear to be a neglected factor when totals are set. Bettors should note that there appears to be a significant relationship between high wind speed and an increasing tendency for actual match totals to not only decrease, but to also go under the quoted totals.

The data since 2003 can be used to find the relationship between average wind speed and the likelihood that the actual game total will fall below the quoted total.

And the best predicted fit from the data for the strike rate of games going under the quoted total when the average wind speed is 15 mph is 54.5%. The percentage of unders then remains consistently above this figure as winds strengthen even more. For example, at average speeds of 17 mph, the likelihood of the match total going under the quote rises to 55.6% and hits 60% at 25 mph.

So once again 15 mph or greater would appear to be the point at which wind becomes a significant and possibly under exposed factor, assuming totals continue to be quoted in a similar way in the future, then bettors have the opportunity to gain an edge.

Weather is likely to be an under represented factor when setting and betting on total lines, especially when markets open and develop early in the week, when weather patterns may be unreliable or partially ignored.

Game day weather and longer term forecasts can be found at such sites as NFL Weather, although as with any prediction, there will still be a degree of uncertainty associated with these forecasts.

However, from past evidence, weather conditions may provide a valuable edge when betting on game totals, with wind speed an obvious, but by no means the only weather related factor to consider in such markets.

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