The wettest races in WEC history, and what the lap chart says about them

By the weather data held in this archive, the wettest race in WEC history is the 2026 Imola round. The hourly values for that race add up to 10.7 millimetres of rain over the race window, with 6.5 mm in the wettest single hour. Toyota Racing won it. Across all 107 races in the archive, counted up to the 2026 Barcelona round, 19 pass the threshold this site uses for a wet race: at least 1.0 mm over the race window.

Those numbers need a careful reading, because the weather data is modelled rather than measured at the track. This story sets out how the rainfall is calculated, lists the wettest races, checks the list against the lap chart, and looks at who wins the races the data flags as wet.

How the rainfall is measured

The archive does not hold official track-condition reports. Its weather comes from Open-Meteo, a public service whose historical archive provides modelled hourly values (a reanalysis, not a rain gauge at the track) for any point on the map. For each event the archive takes the hourly series at the circuit's coordinates and attaches to each race every hour of its scheduled race window, from the scheduled start in local time to the end of the scheduled race length. A six-hour race gets six or seven hourly values and the 24 Hours of Le Mans gets 24 or 25. The race's rainfall figure is the sum of those values.

Two limits remain:

- A modelled hourly value is a smoothed estimate for an area, not a reading at the circuit. A short, heavy shower over the track can be spread thin or missed, and rain a few kilometres away can show up as rain at the circuit. - The window follows the schedule, not the race as run. A race that is stopped early or extended keeps its scheduled window.

So the totals can miss local showers or overstate them. They are good at catching a day of persistent rain and poor at describing what the track was like lap by lap. That is why the sections below check the list against the lap chart.

The ten wettest races

Races with equal totals are ordered by their wettest hour. The years are race dates, so a race from a split season such as 2019-20 is listed under the year it was run.

The totals at the top sit close together: 10.7 mm for the leader and 4.2 mm for tenth place. A 24-hour race has four times as many hours as a six-hour race to collect rain, so a Le Mans total is not directly comparable with a six-hour one.

What the lap chart confirms, and what it does not

The lap chart is an independent check. Rain slows lap times, and heavy rain brings safety cars and red flags, which cut the distance a race covers. Comparing the winner's lap count and the fastest race lap with an earlier edition at the same circuit gives a rough test of whether a race ran in wet conditions. These are closed results, taken from the archive's classifications:

The fastest race lap here is the quickest best lap in each race's classification. At the 2013 and 2017 Fuji rounds, the 2018 Shanghai round and the 2025 Circuit of the Americas round, both measures point the same way: far fewer laps and much slower best laps than the comparison year. The 2013 Fuji winner completed 16 laps in a race scheduled for six hours. The 2020 Spa race also ran shorter and slower than the 2018 edition. At the 2026 Circuit of the Americas round the difference from 2024 is small.

The 2026 Imola round is the clearest exception. It has 10.7 mm of rain in its race window, yet the winner covered the same distance as a year earlier and the fastest lap was in line with the dry 2025 race. The median valid Hypercar lap stayed between 1:34.1 and 1:35.2 in every 25-lap stage of the race. Here the reanalysis and the lap chart disagree.

The two Mexico City races, in 2016 and 2017, have 9.2 mm and 8.4 mm respectively. The archive holds no other WEC race at the circuit, so there is no dry edition to compare them with.

The lesson is simple. Treat the rainfall ranking as a list of candidates, and the lap chart as the evidence.

Dry against wet at the Circuit of the Americas

The clearest like-for-like comparison in the archive is the Circuit of the Americas, where the 2024 race had 0.7 mm of rain in its race window and the 2025 race had 5.4 mm. The table below uses every valid Hypercar lap in the lap chart:

The fastest lap was 11.1 seconds slower in 2025 and the median lap about 25 seconds slower, and the Hypercar field completed a third fewer valid laps. The median moves much more than the best lap because a wet race includes many slow laps behind the safety car and on a drying or flooded track, while the best lap comes from the moment when conditions were least bad.

Who wins the wet races

With those cautions in mind, here is how the 19 races over the threshold split. The counts include every flagged race, including the 2026 Imola round.

Manufacturers. Toyota has won 11 of the 19 wet races. In all, 3 manufacturers have won one. For context, across all 107 races in the archive, Toyota has won 53 and Porsche 20, against 11 and 6 wet wins. The wet sample is small, and a single race moves the shares a long way.

Teams. Toyota Gazoo Racing has the most wet-race wins with 7. Toyota's factory team appears in the archive under two names, and the archive counts them separately: Toyota Gazoo Racing has 7 and Toyota Racing 4. In all, 6 teams have won a flagged race.

Cars. The Toyota TS050 Hybrid has the most wet wins of any car, 6. The next-best total is 5: Porsche 919 Hybrid.

Drivers. Brendon Hartley has the most wet-race wins, 8. The next-best total is 7: Sébastien Buemi. In all, 23 drivers have won at least one of the flagged races. As on the records pages, a driver is credited only if they drove in the race.

The 2026 Imola round, where the reanalysis and the lap chart disagree, counts in these totals for the No. 8 Toyota crew of Sébastien Buemi, Brendon Hartley and Ryo Hirakawa.

Le Mans in the rain data

Le Mans gets a full 24-hour window, one value for each hour of the race. The number of Le Mans races in the archive that pass the wet threshold is 2. The wettest Le Mans is the 2024 24 Hours of Le Mans, with 7.9 mm, won by Ferrari AF Corse. The next wettest is the 2020 24 Hours of Le Mans at 3.6 mm.

For the 2024 race the lap chart agrees. The winning No. 50 Ferrari completed 311 laps, against 342 in 2023 and 387 in 2025. The median valid Hypercar lap was 3:51.7, against 3:36.2 in 2023 and 3:31.4 in 2025, while the fastest valid Hypercar lap, 3:28.562, was close to the other years. That pattern of a normal best lap and a much slower typical lap is what a race with long wet or neutralised periods looks like.

Reading the list

The rainfall ranking is a useful starting point and a weak conclusion. It catches days of persistent rain such as the 2013 and 2017 Fuji rounds, the 2025 Circuit of the Americas round and the 2024 24 Hours of Le Mans, all of which the lap chart confirms. It can also flag a race where the lap chart shows dry pace throughout, as at Imola in 2026.

Official track-condition data from the timing feed would make the list stronger. Until then, read every claim about a wet WEC race on this site as "wet according to the hourly weather data", and check it against the lap chart before it carries any weight. Each race in the top-ten table links to its event page, which holds the full classification.