What must you reckon with when it starts raining after a long period of dry weather?

After a long dry spell, a lot of rubber dust, oil, fuel residue, and general dirt builds up on the road surface. When the first rain arrives, it mixes with this layer and creates a thin “greasy film.” That makes the road noticeably more slippery than usual, especially in the first minutes of rainfall, so you must expect reduced grip, longer braking distances, easier wheelspin, and a higher risk of skidding in curves and when braking.

Bad visibility can also occur immediately when you switch on the windscreen wipers because the first wipes often smear a dry, dirty windscreen (dust, insect remains, and road grime) and the washer fluid may not clear it instantly. In addition, the first rain can create spray and glare from oncoming headlights, further reducing visibility.

The key rule of thumb for similar situations is: the first rain after a dry period is often the most dangerous. Slow down early, increase following distance, brake and steer smoothly, and use washer fluid if the wipers smear. The idea that braking distance becomes shorter is the opposite of what you should expect on that slippery film.