. In a mixed-condition Grand Prix a driver spends part of the race on intermediates and part on slicks. Comparing their own median green-flag lap on each removes the car, the driver and the circuit from the comparison completely. Whatever is left is the weather.
That gave 8 races between 2022 and 2026, and 140 driver records. Wet races are rare, which is why the window has to be this wide.
Green flag laps only, no in-laps or out-laps, nothing from the opening two laps, no deleted laps.
Four checks were set before running it. Full wets must be slower than intermediates, which must be slower than slicks. The intermediate penalty must land somewhere between 5% and 30%, since anything under 2% would mean we were measuring a dry track and anything over 50% would mean safety car laps had leaked in. At least three races with at least six drivers each. And the effect must vary between races, because "wet" covers everything from damp to a downpour. All four passed.
Eleven seconds a lap
2023 Monaco — 17.0% slower, 13.2 seconds a lap
2025 Spa — 14.3%, 15.4 seconds
2022 Imola — 14.3%, 11.7 seconds
2025 Silverstone — 13.6%, 12.5 seconds
2024 Montreal — 13.0%, 10.1 seconds
2024 Silverstone — 11.5%, 10.6 seconds
2023 Zandvoort — 10.1%, 7.7 seconds
2022 Singapore — 8.8%, 9.7 seconds
Spa produces the biggest absolute loss at 15.4 seconds, simply because it is the longest lap on the calendar. A percentage costs more seconds when there are more seconds to lose.
Monaco produces the biggest percentage at 17.0%, and that fits what Monaco is. There is no run-off, the barriers are immediate, and the consequence of a mistake is a wall rather than a gravel trap. Drivers leave more margin there than anywhere, and the stopwatch records it.
The variation between races is the point rather than a problem. A damp track that is nearly ready for slicks and a track with standing water are both "wet", and the 8.8% to 17.0% spread is that difference showing up.
Nobody is quick in the rain
There is a persistent idea that rain is the great equaliser, that it lets a brilliant driver overcome a bad car. The individual records complicate that.
The distribution of wet-weather lap time penalties across all 140 driver records
The range across all 140 records runs from 6.3% to 24.3%. The best single performance still lost more than 6% against that driver's own dry pace.
What rain does is not make anyone fast. It widens the spread between drivers, and it hands out far more opportunities for someone to make a mistake. The equalising happens through chaos and through the value of track position, not because a car becomes competitive that was not.
The tyre nobody wants to use
The three tiers, measured within the same races:
Lap time penalty for intermediates and full wets against slick pace
Slicks — the reference
Intermediates — 13.2% slower
Full wets — roughly 23% slower
That full wet figure comes from only two driver records and should be treated as indicative, not precise. We are reporting it because the gap to intermediates is large and consistent with what the sport says about the tyre, not because two records settle anything.
The reason the sample is so small is itself the story. The modern grid barely uses the full wet. When conditions are bad enough to need it, they are usually bad enough for the race to be neutralised behind a safety car or red-flagged, and by the time racing resumes the intermediate is the better tyre. The full wet has been squeezed into a window that has almost stopped existing, which is a live discussion in the sport and the subject of ongoing debate about whether the tyre earns its place.
What this changes about watching a race
Eleven seconds is the number to hold onto. When a driver stays out on slicks as rain arrives, or gambles on intermediates before anyone else, that is the size of the bet.
The crossover is worth more than any strategy call. Being on the right tyre for two laps is worth more than a perfect pit stop, and it is why teams stare at radar rather than lap charts when the weather turns.
Rain does not make a slow car fast. It makes results unpredictable, which is a different thing.
Percentages travel, seconds do not. Spa lost more seconds than Monaco while being less severely affected. Always check which one you are being quoted.
Method
Data: FastF1, mixed-condition races from 2022 to 2026, being those where at least six drivers set at least four green-flag laps on both intermediates and slicks.
For each driver, median green-flag lap on intermediates against median green-flag lap on slicks, within the same race.
Excluded: in-laps, out-laps, laps 1 and 2, any lap not under green flag, deleted laps.
Sample: 8 races, 140 driver records.
Known limitation: a drying track is not a constant. Intermediate laps tend to come earlier when the track is wettest, and slick laps later when it is driest. That means these figures capture the full contrast between the wet and dry phases of a race, which is the practically useful number, rather than the penalty at one fixed level of wetness.
The full wet figure rests on 2 driver records. It is labelled as indicative everywhere it appears and should not be quoted as a precise value.
Races where the whole event was wet, with no slick running, cannot be used by this method and are excluded.
