iRacing 2026 Season 4: How Weather Rerolls Work in Official Races

iRacing has significantly expanded its new Weather Reroll system for 2026 Season 4, with 34 official Sports Car and Formula Car series now regenerating weather conditions for every individual race session. Instead of every race during a week sharing the same generated weather configuration, eligible series can now produce a different forecast from one race to the next. For the included Class C and higher series, precipitation is unrestricted throughout the season, while selected Class D series retain a two-week precipitation limit despite also receiving per-race weather regeneration.

The change follows iRacing’s Weather Reroll tests during the preceding Week 13. At that stage, the Ferrari 296 Challenge and GT3 Challenge Fixed regenerated their weather once per day, while the Porsche Cup generated new conditions for every race, allowing iRacing to compare different approaches before the regular season began.

iRacing originally described these experiments in its August 2026 Development Update as a measured test rather than a service-wide overhaul. Following the Week 13 trial and member feedback, the company has now opted for the more aggressive per-race approach across a much larger selection of official series.

How iRacing’s New Per-Race Weather System Works

The fundamental change is that the weather configuration is no longer tied to every race of an eligible series for an entire week. Each individual race session receives a newly generated weather forecast, meaning two consecutive races at the same circuit can potentially offer substantially different conditions.

That does not mean every race will feature rain. iRacing’s Forecasted Weather system uses parameters including the circuit, simulated date and historical weather information to create plausible conditions, while the displayed forecast itself remains a prediction rather than a guarantee of exactly what will happen during the race.

This creates variability even when precipitation never arrives. Temperature, cloud cover, wind and other atmospheric conditions can differ between races, while wet-capable combinations can potentially move between completely dry conditions, changing grip levels and more substantial rain scenarios.

For the Class C and higher series included in the rollout, precipitation is unrestricted across the entire 12-week season. This means rain can be generated during any week where the car and circuit support it, rather than rain opportunities being restricted to a small selection of predetermined rounds.

The rule is more conservative for included Class D series. Their weather will still regenerate for every race, but precipitation remains restricted to two weeks during the season. The other weeks can still receive regenerated weather conditions without introducing rain.

34 Official Series Receive Weather Regeneration

The initial implementation covers some of iRacing’s most frequently raced road categories, including GT3, IMSA, Porsche Cup, Super Formula, GT4, LMP2, LMP3, Mazda MX-5, Ferrari 296 and several regional championships.

iRacing published the rollout according to each series’ GMT race slot. The complete initial list is as follows:

One notable detail in the published list is Formula C Super Formula Lights Fixed. The Fixed series is explicitly included, while the corresponding Open series does not appear in iRacing’s initial rollout. Unless iRacing subsequently updates the list, the Open version should therefore be considered unchanged.

The same principle applies throughout the service. If a series does not appear on iRacing’s published list, its existing weather configuration remains unchanged.

Why This Is a Major Change for Official Racing

iRacing introduced its Tempest dynamic weather system with the 2024 Season 2 build, bringing rain, evolving track moisture, radar information and forecast-based weather to the simulator. However, the way weather was deployed in official competition meant that drivers could often become familiar with the general conditions expected throughout a race week.

Per-race regeneration changes that preparation model considerably. A driver can no longer assume that the conditions encountered in one GT3, IMSA or Porsche Cup race will necessarily be reproduced in the next session of the same week.

That makes adaptability more important. Drivers may need to prepare for different track temperatures, changing grip, wet-weather lines and potentially tyre decisions rather than optimizing exclusively around one repeatedly encountered weather scenario.

The impact could be particularly significant in longer races. A regenerated forecast can create conditions where the circuit begins dry and evolves toward rain, starts wet and dries, or remains dry while atmospheric conditions change around it, creating more strategic variety between otherwise identical races.

Importantly, a percentage shown in the forecast remains exactly that: a forecast rather than a scripted weather timeline. A substantial precipitation probability does not guarantee identical rainfall, timing or track conditions every time a session is generated.

iRacing Plans to Expand the System Further

The 34-series implementation is not intended to be the final scope of Weather Rerolls. iRacing says it will monitor the system throughout Season 4, including member feedback and the overall racing experience, before deciding how aggressively to expand the technology.

The company has specifically mentioned Oval and Dirt racing as potential future areas for per-race weather regeneration. That does not confirm that rain will suddenly become available on every oval or dirt combination; rather, it confirms that iRacing is evaluating how regenerated weather conditions could eventually be applied beyond its current Sports Car and Formula Car rollout.

There is also room for the implementation itself to evolve. iRacing initially tested both per-race and per-race-day regeneration during the development process, meaning Season 4 should provide substantially more data on how unpredictable conditions affect participation, race quality and driver behaviour.

For now, the practical change is substantial. In many of iRacing’s major road racing series, entering the next official race no longer means expecting the same weather configuration experienced in the previous one.

That places more emphasis on reading the forecast, adapting during the session and preparing for a wider range of track conditions. After more than two years of development around the Tempest system, Season 4 represents one of iRacing’s biggest changes yet to how dynamic weather is actually used in regular official competition.

New drivers can access the service through an iRacing membership.

See you on the track!