Have you ever noticed that there are more crashes on the roadways when it rains for the first time after a dry spell?

That first rain produces more fatal crashes than a typical rainy day. A lot of the reason has to do with what’s already on the roads before the rain falls.

During a dry stretch of weather, there is no rain to wash the sediment, oil and grease away. Over time, the buildup on the roads accumulates into a greasy layer.

When it rains for the first time, the greasy layer rises to the top, forming a slick surface for drivers.

Watch the video above to see exactly why this occurs.