Tenerife,especially in the South, and the other Canary Islands are sometimes hit by dust clouds from the Sahara desert brought here on hot, dry winds, and this phenomena is known as La Calima, and may last for days.
A calima makes the sky and air look as if it is full of fog or mist but may have a yellowish tint to it. Unlike fog it is very dry and can be experienced whilst the sun is high in the sky, although the light is severely cut out as can be seen in the photo above, which was taken around 3pm in the afternoon.
The dust carries microbes that some people are allergic to and it may make respiratory problems worse. It also settles on cars and other surfaces and can prove a nuisance.
However, the phenomenon is only temporary and normal sunshine always returns after it stops.