The wettest races in WEC history, and what rain does to lap time

The 2025 6 Hours of COTA was the wettest race in the recorded WEC era. Hourly weather observations across the six-hour race window logged 23.8 millimetres of cumulative rainfall, including a single hour with 13.2mm. The race ran six safety-car periods, a forty-minute red flag, and fewer than three hours of green-flag racing time across the full event. Porsche Penske Motorsport's #6 (Matt Campbell, Kévin Estre, Laurens Vanthoor) won. That is the only WEC race in recent memory where the winning crew did not include a Toyota driver across a top-ten weather-impact pool.

The pre-2025 record sat at 8.2mm at Fuji 2013 (Round 7), which Toyota Racing won with Nicolas Lapierre, Alexander Wurz and Kazuki Nakajima. Almost three times the rainfall later, COTA 2025 reset the ceiling. The article is the full ledger of every race the weather dataset flags as wet, what rain does to Hypercar lap time, and which drivers have made their careers on those wet weekends.

A note on the data before the tables: our weather records come from Open-Meteo hourly reanalysis matched to race-window observation timestamps, four to five samples per six-hour race, captured at the circuit's geographic coordinates. The samples are accurate at the hour but cannot resolve short-duration squalls between the observation times. We caught the heaviest hours of every race in the list below, so the rankings are robust; the absolute totals are conservative.

The top ten wettest WEC race weekends

A few patterns are visible without further analysis. COTA 2025 is an outlier of a kind WEC has not seen before: it logged more rainfall in one race window than the next four wet races combined. The pre-2025 list is heavily Toyota, both at the team level (Toyota Racing or TOYOTA GAZOO RACING in 8 of the top 10) and at the driver level (Sébastien Buemi in 3 of the top 10 wins alone). Le Mans 2021 is the only 24-hour race in the top 10, which is partly a function of the longer race window dilution and partly because Le Mans rains are usually localised.

What rain actually does to Hypercar lap time

The cleanest controlled comparison the WEC dataset offers is COTA 2024 (dry, six hours) versus COTA 2025 (the 23.8mm-event we just described). Same circuit, same race format, same Hypercar regulations, same chassis from every factory, BoP within ten kilos either way. The lap data:

The pace impact is the median, not the best lap. The best lap moves +11.1 seconds because the entire field has to use wet tyres at all times the green flag is out. The median moves +25.4 seconds because the race spent most of its scheduled six hours under safety car. The number of Hypercar laps completed in 2025 was 33% fewer than 2024, almost exactly the proportion of the race that ran under green vs neutralisations.

Stretch the comparison out across all Hypercar Le Mans 24h races (where the same chassis run across multiple years with varying weather), and the same pattern shows up at smaller magnitude:

The 2024 Le Mans race is the interesting outlier. Only 0.8mm of rain registered in our hourly samples, but the median pace was a full 10 seconds slower than 2025's dry edition. The reason is timing: the rain that did fall came in two short windows that triggered red flags. Our weather samples caught the totals but not the chaos. The lap data is what tells you the race was wet. This is the cleanest reminder in the dataset that hourly rainfall totals are a coarse proxy for the actual on-track conditions, and that you should always cross-check rainfall against median lap-time degradation when reasoning about a "wet race".

Why Toyota wins when it rains

Eight of the top ten wet WEC races on record were won by the Toyota factory programme. The pattern holds across two regulation eras (LMP1 hybrid in 2012-2020, Hypercar in 2021-2025), three chassis generations (TS030, TS040, TS050, GR010), and the team's rebrand from Toyota Racing to TOYOTA GAZOO RACING and back to Toyota Racing for 2026.

The three causal threads, in order of how much the data supports them:

Driver pairing. The career wet-race win counts:

Buemi is the all-time wet-race leader in the WEC, with wet wins at Silverstone 2014, Fuji 2017, Spa 2019, and Imola 2026. The #7 Hypercar pairing of Conway / Kobayashi / Lopez accounts for three top-five wet wins in 2019-2021 alone. The Hartley two-pack stretches across Porsche LMP1 and Toyota Hypercar; he is the only driver to win wet races for two different top-class manufacturers.

Chassis. Both the Toyota TS050 (2016-2020) and the GR010 (2021-2025) used hybrid power-unit deployment maps that allowed energy recovery on the lift-and-coast phases through corners. In wet conditions where the brake-traction balance is fragile, that hybrid behaviour gives a smoother torque delivery than a non-hybrid car. The Porsche 919 Hybrid had a comparable system in 2014-2017 but was never on the grid for one of the top-five wettest races (Porsche was at Mexico 2016 which made the list, but 1.1mm of rain is the lower end of the wet scale).

Strategy book. Toyota's race operations team has a long-standing reputation for calling the tyre-change windows earlier than rivals in wet-to-dry and dry-to-wet transitions, accepting a small loss of clear-air pace to avoid a large loss of in-traffic pace on the wrong rubber. This is anecdotal from team radio archives rather than directly measurable from our dataset, but the LMP1-era pattern is consistent enough across 2014-2020 to read it as an operational edge.

The Le Mans rain trilogy, 2021 to 2024

Three of the most recent five 24-hour races have had measurable rain across the race window, and each one produced a different outcome:

Le Mans 2021 (2.2mm, the wettest 24h on record). Toyota won (the #7 of Conway / Kobayashi / Lopez), in their last LMP1-class-era win at the circuit. The rain came in two windows on the Sunday morning, both around the lap-time degradation peak.

Le Mans 2023 (0.6mm). Ferrari won its first Le Mans since 1965 with the #51 (Pier Guidi / Calado / Giovinazzi). The rain was a brief late-Saturday squall that caught Toyota out on the wrong tyre choice and gave the #51 Ferrari a 32-second cushion it never lost.

Le Mans 2024 (0.8mm in the samples, but the lap data shows median pace +10 seconds versus 2025). Ferrari won again (#50, Fuoco / Molina / Nielsen), this time benefiting from a conservative tyre strategy that absorbed two red-flag windows in the Saturday-night and Sunday-morning rain pulses. The Ferrari #51 was set to win until a brake-by-wire issue cost the lead.

The pattern across these three: rain at Le Mans does not produce a wet-specialist win. It produces a strategy win, where the team that calls the right tyre at the right red-flag restart wins. Ferrari has gone from one Le Mans win in fifty-eight years to three consecutive Le Mans wins by being on the right tyre in three different weather scenarios.

What COTA 2025 actually broke

The Porsche Penske win at COTA 2025 is the first Hypercar-class wet-race win in WEC history by a team other than Toyota or Ferrari. Hypercar-era wet races by winner:

Six wet Hypercar races, three winners. Toyota has three (continuity with the LMP1 era). Ferrari took the two wet Le Mans editions immediately after re-entering the class (2023, 2024). Porsche took the heaviest-rain race the WEC has ever recorded.

The reason COTA broke from the Toyota/Ferrari pattern was the rainfall regime itself. At 1-4mm of light intermittent rain, the difference between a fast lap and a slow lap is driver feel and traction recovery on the throttle. At 23mm of cumulative heavy rain with standing water, the difference is whether the safety car comes out at the right time to compress the field. The latter is decided by the FIA race director, not by the car or the driver pairing.

Porsche won the race by being on the right tyre at the right safety-car restart, which is the same mechanism that won Ferrari Le Mans 2023 and 2024. When the rain stops being a pace input and becomes a strategy input, the wet-specialist advantage at the driver and chassis level disappears, and the result turns on the strategy call at the restart.

What the 2026 season is signalling

Round 1 of 2026 (Imola) was the fourth-wettest race in our dataset at 3.6mm, the first rain-affected race of the new regulation cycle. Toyota Racing won it with Buemi / Hartley / Hirakawa. Buemi's fourth career wet-race win, the #8 GR010-cum-TR010's continuation of the Toyota wet-race pattern. The new TR010 bodywork update appears not to have broken the underlying hybrid-traction advantage that Toyota has run since 2012.

If 2026 follows the historical pattern, the next likely rain-affected races are Spa or Fuji. Both are on the calendar (Spa in May, Fuji in September). Across the full WEC era Toyota wins 8 of 10 wet races; across the Hypercar era only it is closer to 3 of 6. Whether the new Ferrari 499P aero update or the BMW M Hybrid V8 can take a wet win at one of those weather-likely venues is the most interesting open question of the second half of the season.

If the next wet WEC race produces a winner that is not Toyota, Ferrari, or Porsche, the wet-race era as a five-team game is genuinely open for the first time in fourteen seasons.