| | | | | | |

How Realistic is The New iRacing Weather System?

Formula Ford in the wet (iRacing)

Featured image: Formula Ford in the wet!

It must be tough for sim racing developers to nail the wet weather experience.

In motorsport, so many new variables are introduced when the heavens open, forcing the driver to constantly re-evaluate the situation. If realism is what’s targeted, then wet lines, standing water, persistent grip level changes, and reactive tarmac barely scratch the surface of considerations.

Raidillon to Eau Rouge in the wet
Raidillon to Eau Rouge in the wet

This is probably why popular PC platform iRacing felt it needed to adjust the forecast for its Tempest Weather System’s introduction, delaying the long-awaited appearance of wet weather late last year.

It finally appeared in early March, and thankfully, a decade of personal real-racing experience in the UK translates to a decade of wet weather driving, giving me plenty of references to help analyse its authenticity.


As the clouds roll in, an all-too-familiar feeling presents itself. “We expect light rain soon” exclaims Jeff. Now you know things are going to get dicey. You can feel the temperate change on the back of your neck, as darkness descends around the circuit. iRacing immediately succeeds at setting the mood.

The Wet Line

As the surface retains water, grip levels drop and iRacing of course simulates this happening. Perhaps, this aspect is a little rudimentary; The average grip level feels fairly linear from dry to wet, whereas in reality, on many occasions you will have just as little grip with the wet tyres on a greasy circuit as you would on a fully wet circuit. The overall wet weather grip levels are arguably a touch high on average, but this is being very picky as in truth, some circuits with certain types of tarmac will give you incredibly high levels of grip in wet conditions. There is huge variety from circuit to circuit, therefore iRacing has seemingly looked for a compromise and I don’t feel there is much ground for complaint.

When it comes to grip variation across a single lap, however, the Tempest Weather System appears to have set a new standard. In wet conditions, the fastest way around a circuit is rarely the regular dry racing line it’s often the opposite.

AI F4 cars taking wet lines
AI cars avoid the apex like the plague (wet lines / Oulton Park / F4)

Rain helps extract oil from rubber on the racetrack, and the racing line will always have far more rubber. More rubber means more grip in the dry, but more oil in the wet, and if you know anything about oil… This results in higher levels of grip away from the regular racing line, creating a new ideal ‘wet line’ that will often see the fastest drivers braking in the middle of the road, and searching for grip on the outside of a corner away from any apices. iRacing simulates this phenomenon better than any other title out there.

GR86 onboard (wet)
Time for some science

To experiment, I drove around Brands Hatch Indy in a Toyota GR86 using the regular dry line, before switching to the wet line that had helped me gain a real-world MX-5 pole position in similar conditions. The wet line was 1.5 seconds faster.

Then, another experiment, heading for Spa-Francorchamps in the F4 car. This time I also wanted to see the effectiveness of the wet baseline setup. A frightening six seconds of lap time were gained by switching from the dry line to a wet line and a dry Spa setup (with wet tyres) to the baseline wet setup. Is this massive swing realistic?! Absolutely.

Wet lines at Spa
Wet lines at Spa – Searching and finding the grip on the outside of Le Fagnes. Try it yourself!

Standing Water

The more visual aspect of wet weather racing is standing water.

Something other sims have gotten right in the past, it’s perhaps easier to simulate and more spectacular for the casual racer than an authentically developing wet line. iRacing immediately tops the list yet again, with a panic-inducingly realistic sensation of aquaplaning and wet-weather lock-ups. The force feedback goes light, sound dissipating as you helplessly careen towards everything but the corner you aimed for. This forces you to drive on full alert, not only searching for grip but avoiding puddles (and painted lines) as if they were land mines.

As you plot the fastest way around the track, wincing at every sudden snap of oversteer, you genuinely forget this is virtual. The standing water even collects in the same spots as in real life… It’s breathtaking.

Kerbs and White Lines are lethal, as they should be
Kerbs and White Lines are lethal, as they should be

Attention to Detail

A clever inclusion is the reactive drying line as the rain dissipates. This line isn’t pre-determined or generic; The areas of the circuit that are driven over by the most cars will dry the quickest, as it would in real life. This means every single wet race will offer up something different. When following, the spray on iRacing blinds you as it should as well. In fact, on some occasions, it’s too much.

When the track is merely damp instead of fully wet, there is a low trail of spray but nothing more. On iRacing however, even when driving on a ‘very damp’ track, the amount of spray is a little too high. Maybe the issue lies in the terminology.

Rear F4 spray
The word ‘damp’ feels like classic British sarcasm in this context…

Another thing that’s arguably ‘too much’ is the grip level on wet grass in comparison to the real thing. On the many occasions I found myself skating across the grass, it was always surprisingly straightforward to regain control. Maybe this is one area of wet weather where enjoyment is prioritized over realism.

Sunshine and Rainbows

Racing in the rain in real life isn’t a choice. It’s an inconvenient, uncontrollable component of nature that motorsport tolerates. Sure, it’s fun to watch from the comfort of a warm and dry sofa, but for the driver, it’s challenging, dangerous, and requires a lot of mental strength.

Rain in sim racing is a choice. It needs to balance realism with enjoyment, because fun, in whatever form, is what sells. Based on the reasons I’ve outlined above, I feel iRacing has nailed that balance. It provides enjoyment from the challenge itself; searching for the grip, holding the car in a beautiful slide, making moves around the outside, and taking advantage of others’ misfortune. But if you do get it wrong yourself, it doesn’t want your race to be over like it might be in real life. Skills will be rewarded with great results, but for those who are intimidated by it, you can get out there, learn, push the limits, exceed the limits, and, crucially, there’s a good chance of getting back on track. Hopefully, this encourages longevity within the community, because this implementation of rain deserves to be used and celebrated.

Well done iRacing. This is magical

How Realistic is The New iRacing Weather System?