What is Saharan dust?
Saharan dust is a mixture of sand and dust from the Sahara, the vast desert area that covers most of North Africa.
How does it get to the UK?
As in other parts of the world, the wind can blow strongly over deserts - whipping up dust and sand high into the sky. If the winds in the upper part of the atmosphere are blowing north, the dust can be carried as far as the UK.
Once it is lifted from the ground by strong winds, clouds of dust can reach very high altitudes and be transported worldwide, covering thousands of miles.
In order for the dust to get from up in the sky down to the ground, you need something to wash it out of the sky - rain. As raindrops fall, they collect particles of dust on the way down. Then when the raindrops land on something and eventually evaporate, they leave behind a layer of dust.
Saharan dust is relatively common in the UK often happening several times a year when big dust storms in the Sahara coincide with southerly wind patterns. In certain weather situations, Saharan dust can also affect air pollution and pollution levels.