Weather and the NFL
RoryHoughton-Berry,EdwinPark,KathyPierce
Intro
•  HowmuchchancedidtheSea;leSeahawks
havechanceofwinningthe2016Wildcard
PlayoffgameinfrigidweatherinMinnesota?
•  WilltheRams’relocaIonfromSt.LouistoLos
Angelesgivethemmoresuccess?
Intro
•  Howdoesrainaffectrushdefense?
•  Dopassheavyteamsstruggleinthewind?
•  IspassdefensemoreeffecIveincoldor
warmtemperatures?
•  Howdoessnowaffectteamswithhighpoweredoffenses
ResearchQuesIon
How does weather affect different NFL teams according
to their strengths and weaknesses?
The Data
•  Game-by-gamescoreandweatherdataforthe2009-2013seasons
•  Temperature
•  WindSpeed
•  CondiIons
•  Expectedpointscontributedbyoffenseanddefensefromprofootball-reference.com
The Data
•  ColdestGame:2014NFCWildCard
Playoff49ersatPackers(4oF)
•  Ho;estGame:2010regularseason
week1BroncosatJaguars(91oF)
•  WindiestGame:2009regularseason
week4Ramsat49ers(27mph)
The Data
MiamiDolphins(78.9oF)
GreenBayPackers(42.6oF)
Preliminary Analysis
WeatherEffectsonPointsperGame
WeatherAspect
Es-mate
P-value
Temperature
0.011
0.65
WindSpeed
-0.26
0.0009
Rain
-1.71
0.28
Snow
5.61
0.15
FairWeather
2.69
0.0008
Indoors
3.27
0.0001
Turf
2.44
0.0014
Preliminary Analysis
WeatherEffectsonPointDifferencebetweenHomeandAwayTeams
WeatherAspect
Es-mate
P-value
Temperature
-0.068
0.012
WindSpeed
0.01
0.91
Rain
3.72
0.03
Snow
-4.20
0.32
FairWeather
-1.51
0.08
Indoors
0.81
0.38
Turf
3.49
0.00003
Preliminary Analysis
WeatherEffectsonHomeScoreandAwayScore
WeatherAspect HomeTeam
Es-mate
P-value
AwayTeam
Es-mate
P-value
Temperature
-0.03
0.13
0.04
0.03
WindSpeed
-0.13
0.03
-0.14
0.02
Rain
1.01
0.40
-2.72
0.02
Snow
0.70
0.81
4.91
0.08
FairWeather
-2.10
0.0005
-0.59
0.31
Indoors
2.04
0.001
1.23
0.05
Turf
2.97
0.0000003
-0.53
0.35
Preliminary Regression Model
WeatherEffect
DependentVariable
Es-mate
P-value
Temperature
PointsperGame
0.092
0.04
HomeScore
-0.087
0.009
WindSpeed
AwayScore
-0.12
0.08
Rain
PointDifferen-al
3.25
0.03
AwayScore
0.031
0.08
PointDifferen-al
2.23
0.06
HomeScore
1.77
0.04
PointsperGame
0.082
0.03
HomeScore
0.058
0.03
AwayScore
0.030
0.03
Indoors
Differencefrom
AverageTemperature
forAwayTeam
Preliminary Findings
•  GoodweathercondiIonshelpbothteamsscoremorepoints
•  BadweathercondiIonsincreasethepointdifferenceofthe
HometeamovertheAwayteam
•  StadiumswithTurfoverGrasshelpbothteamsscoremore
points
•  IndoorstadiumscomeupwithconflicIngresults,butthey
appeartoprimarilyhelpthehometeam
Our Model
•  CharacterisIcsofagame’shome&awayteams:
•  PassOffenseEXP(expectedpointscontributedbypassingoffense)
•  RushOffenseEXP
•  PassDefenseEXP
•  RushDefenseEXP
•  AverageTemperaturewhenplayingatHome
•  Weatherdata:
•  TypeofWeather={Fair,Rain,Snow,Indoor}
•  PlayingSurface={Grass,Turf}
•  Temperature
•  WindSpeed
Our Model
•  TrainingSet:2009-2012seasons
•  TestSet:on2013season
•  Model:
•  ExtendedversionofregularizedBradley-TerryModel
•  Features:{PassO,RushO,PassD,RushD,AvgTemp} +{PassO,RushO,PassD,RushD}X{Temperature,WindSpd,Fair,Rain,Snow,Indoor,
Grass,Turf}
•  LassoRegression
Our Findings
•  Forhometeams,wecouldpredictthenumberofpointsscoredwitha
mean-squarederror(MSE)of9.3points.
•  Forawayteams,wecouldpredictthenumberofpointsscoredwith
MSEof8.4points.
•  ForscoredifferenIals,wecouldpredictwithanaccuracyofMSE=
11.3points.
Home Team Weather Effects
Helpshometeamscoremore
points:
•  Rain(Passing)
•  Turfplayingsurface(Passing)
•  WarmerTemperatures
(Rushing)
Makeshometeamscorefewer
points:
•  Warmertemperatures
(passing)
•  Playingindoors(passing)
Away Team Weather Effects
Helpsawayteamscoremore
points:
•  WarmerTemperatures
(both)
•  FairWeather(passing)
•  Turfplayingsurface(rushing)
Makesawayteamscorefewer
points:
•  Facingagoodpassdefensein
faircondiIons
Weather Effects on Score DifferenFal
Helpshometeamscoregain
morescoredifferenIal:
•  Warmertemperatureshelp
rushdefense
•  Hometeam’spassoffensein
rainyweather
•  Hometeam’spassdefensein
snowyweather
Makeshometeamscorelose
scoredifferenIal:
•  Awayteam’spassoffensein
fairweather
LimitaFons
•  Detaileddatacanbehardtoobtain(manyNAs)
•  HardtoaccountforvariaIoninhomefieldadvantage
•  EXPscanbenegaIve,socanbedifficulttointerpretinteracIons
•  PossiblemulIcollineariIes
•  Modeldoesn’taccountforinteracIonsbetweenweathercondiIons
SuggesFons for further research
•  HowweatherchoiceaffectsplayselecIon
•  Howwelldifferentteamsadapttheirplayingstyletotheweather
•  HowImezonechangesaffectteamperformance
•  Whetherteamswhohavetotravelmoreintheregularseasonhave
moreorlessflexiblegameplans
References
•  pro-football-reference.com
•  NFLsavant.com
•  NFLweather.com
QuesFons?