Research
Rain, wet grounds and AFL scoring
Everyone assumes rain kills AFL scoring. Almost nobody publishes the number. We pulled hourly venue rainfall for every AFL match we could place since 2004, matched it to the final scores, and split the games by how much rain actually fell around the first bounce. Here is what the archive says, including the sample sizes and the size of the effect at the wet end.
The headline
Rain does suppress AFL scoring, and the effect is bigger than most people assume. Across 4,349 matches from 2004 to 2026, games on a dry ground averaged 178.1 combined points against 160.8 on a wet one — a gap of 17.3 points. Once it is actually raining, each extra millimetre in the match window is worth about 3.5 points off the total.
Dry ground average
178.1
+2.4 vs season average
3,178 games
Damp ground average
170.4
-3.9 vs season average
870 games
Wet ground average
160.8
-13.6 vs season average
301 games
Ground state and combined score
| Ground state | Games | Avg combined points | Median | Spread (SD) | Vs season avg |
|---|---|---|---|---|---|
| Dry groundNo measurable rain in the match window or the 24 hours before it | 3,178 | 178.1 | 178.0 | ±32.7 | +2.4 ± 0.5 |
| Damp ground0.1–0.5 mm in the match window or the 24 hours before it | 870 | 170.4 | 169.0 | ±34.8 | -3.9 ± 1.1 |
| Wet ground0.5 mm or more in the match window or the 24 hours before it | 301 | 160.8 | 161.0 | ±33.8 | -13.6 ± 1.8 |
The last column compares each group with the average total of the same season, which strips out the long-term decline in AFL scoring. The wet-ground shortfall survives that adjustment at -13.6 points, roughly 8 times its own standard error — not a rounding artefact.
How much rain it takes
| Rain in the match window | Games | Avg rainfall | Avg combined points | Vs season avg |
|---|---|---|---|---|
| No rain (under 0.1 mm) | 3,374 | 0.00 mm | 177.5 | +1.7 |
| Trace (0.1–0.5 mm) | 489 | 0.21 mm | 170.5 | -2.3 |
| Light (0.5–2 mm) | 360 | 1.00 mm | 168.4 | -6.2 |
| Moderate (2–5 mm) | 102 | 2.89 mm | 160.8 | -15.5 |
| Heavy (5 mm+)thin sample | 24 | 7.80 mm | 139.5 | -30.8 |
The gradient is the point. Scoring falls step by step as the rain gets heavier rather than jumping at one arbitrary cut-off, which is what a real effect looks like. Any band under 100 games is marked thin and should be read as direction only — the heavy band in particular rests on a handful of matches.
The wet-end coefficient
Points per mm (rain games)
-3.5
season-adjusted slope
975 games with 0.1 mm or more
Unadjusted slope
-3.4
same games, no season control
Average 0.97 mm, heaviest 25.3 mm
Whole-sample slope
-5.0
r = -0.123
All 4,349 games including dry ones
Restricting the regression to games that actually saw rain is the honest version: the slope across all matches is steeper only because thousands of dry games anchor one end of the line. Among wet games, each additional millimetre of match-window rain is associated with about 3.5 fewer combined points, and the relationship flattens out past roughly 5 mm — by then the surface is already as slippery as it is going to get.
A coefficient is not a forecast. The standard deviation of totals inside every group sits around 33 points, so rain moves the average without deciding any single game.
Method and limits
- Source: AFL match archive (4,349 completed games, 2004–2026) joined to hourly Open-Meteo reanalysis at each venue's coordinates, in venue-local time.
- Measure: combined final score. Rainfall is the match-window total, with the prior 24 hours used to classify ground state.
- Excluded: games whose venue could not be resolved in the archive, and games without a final score. Nothing is excluded on the basis of the result.
- Not controlled: wind, temperature, roof state, ground drainage quality, team strength and finals context. Those cuts come next.
- No closing totals are available for these matches, so this study reports scoring, not Over/Under hit rates. We will not publish hit rates without the lines.
Data generated 2026-09-07. Numbers refresh as the weekly venue-weather top-up runs; corrections are dated and published on this page.
Live venue weather and game-time reads for every match on the slate.
See today's AFL conditionsFrequently asked
What counts as a wet ground here?
Rainfall recorded at the venue itself. We take the hourly reanalysis rainfall over the match window plus the 24 hours before the first bounce. Under 0.1 mm is dry, 0.1 to 0.5 mm is damp, and 0.5 mm or more is wet. It is a rainfall measure, not a groundskeeper report — a ground can drain well and still be counted wet here.
Where does the weather come from?
Open-Meteo historical reanalysis, pulled hour by hour at each venue’s own coordinates and converted to the venue’s local time, then matched to the AFL match archive by match. Every completed game from 2004 onwards that we could place at a known venue is included — no games dropped for being inconvenient.
Why adjust for the season?
AFL scoring has fallen over the two decades in the sample, so a raw comparison can mistake era for weather. Alongside the raw averages we show each group against its own season’s average total, which removes that drift. Rain frequency is essentially flat across the period, so the adjustment barely moves the numbers — which is itself reassuring.
Does this tell me to bet the Under when it rains?
No. It describes what has happened, not what a bookmaker’s line already accounts for. The market prices obvious rain, our sample carries no closing totals for these games, and single-game variation dwarfs the rain effect — the spread of scores inside every group is around 33 points. Use it as context: check the weather before you bet.
What are the limits of the sample?
Heavy-rain games are rare: the heaviest band holds only a couple of dozen matches, well under our 100-game reliability floor, so that row is marked thin and should not be read as a precise number. Wind, roof state and venue drainage are not controlled for in this cut.