Between rain events, fine dust carried over from the Sahara desert settles on road surfaces. When the first drops of rain hit, that dust mixes with water to form a thin, slick film, almost like a layer of wet clay, before it has a chance to wash away.
This film dramatically reduces tire grip, especially in the first 10–20 minutes of a shower.
The riskiest window is right at the start of rainfall, before the dust has been rinsed off the surface. Once a shower continues steadily for a while, the dust washes away and grip generally improves.
So counterintuitively, a light drizzle after a dry spell can be more dangerous than a longer, heavier downpour.
Q: Which roads and situations are the riskiest?
- Roads that have gone several days or weeks without rain (dust has had time to build up)
- Painted lines, crosswalks, and manhole covers, which get even slicker
- Roundabouts and curves, where braking and cornering forces are higher
- Rural roads with less traffic to naturally clear the dust
Q: Does this affect scooters and motorbikes more than cars?
Yes, significantly. With only two contact points and less weight pressing the tires down, motorbikes and scooters lose traction much faster on a dusty, wet surface. If you ride in Ibiza, treat the first few minutes of any rain shower as black-ice-level caution, particularly when braking or leaning into turns.
Q: What should drivers do to stay safe?
- Slow down noticeably as soon as rain starts, even if it looks light
- Increase following distance — braking distances can double on dust-slicked roads
- Avoid sudden braking or sharp steering inputs in the first few minutes of rain
- Be extra cautious on painted road markings and roundabouts
- If riding a scooter or motorbike, consider waiting a few minutes for the initial dust film to clear if you can
Q: Does this only happen during visible “calima” (hazy sky) events?
No, dust can accumulate gradually and invisibly over dry weeks even without a dramatic hazy-sky calima event. You don’t need to see a dust cloud in the forecast to be at risk; any first rain after a dry stretch carries some of this danger.
Q: How can I check if conditions are likely to be risky?
Watch for two signals together: a dry spell of several days or more, followed by the start of rain. If both apply, treat the first 15–20 minutes of driving as high-risk regardless of how light the rain looks.