Hot, dry winds carrying dust from the Sahara Desert are known as Calima. The winds can lift millions of tonnes of dust and fine sand up to 6km (3.7 miles) into the atmosphere, colouring the sky orange and turning rainwater a muddy brown colour. The suspended particles can be carried thousands of miles on atmospheric currents. When they reach lower altitudes, they can reduce visibility and cause respiratory issues.
Calima mainly affects the Canary Islands, but if conditions are right the dust can be carried all the way to the Mediterranean or even Northern Europe, including the UK.