Calima is the name given to the fine particles of sand which are blown in from the Sahara and which hang in the air creating a fog-like atmosphere. When the wind blows in off Africa it hits the south of the island first and worse but ironically, it’s harder to spot in the south than it is here in the north. For one thing, the wind is a more prominent feature in the south than it is in the north and for another, views of Mount Teide from the south are less than impressive and as the calima usually hangs at height, it’s more difficult to see unless it’s a particularly dense one. For us here in Puerto de la Cruz, we have only to step onto our terrace and look towards the mountain to know that we are in the grip of yet another calima.

But you don’t need visual signs to tell you when calima is present. You know it’s calima when you step outside and it feels like someone is blasting a hair dryer in your face. Even if the wind has dropped, as it usually does after it’s deposited the sand into the atmosphere, you’ll notice a sudden and marked hike in the temperature – another sure sign the sand has arrived.

Although it’s sometimes referred to as a sand storm, it’s not the sort of storm you see in Sahara movies where, stand still for more than a few minutes and you’ll be turned into a sand sculpture. Calima is more subtle than that. To the eye it appears like a fine fog which cloaks everything at distance and creates a ghostly pall over mountains.

As a hiker, calima is something to be avoided. The fine particles of sand are notoriously irritating to pulmonary weaknesses and asthma sufferers are best staying indoors until the worst of the dust has passed which usually takes about three days or a change in wind direction. Once it moves off, rain often follows and deposits a dirty film of sand across everything. But this winter the post-calima rains have never appeared.

Last week we had scheduled a walk for Friday which we couldn’t change without setting off a whole domino effect of disrupted arrangements so, although the calima had arrived on Thursday night, we still went hiking on Friday, something we wouldn’t normally do. Luckily, our hike was at coastal level and for much of it, we were unaware of the presence of calima. Had we planned a hike at altitude, we would have had to postpone it, regardless of the inconvenient circumstances.

So next time you’re planning to go walking on Tenerife and you experience a sudden hike in temperature, the appearance of fog or a hot wind, look at the calendar, if it’s Thursday, it’s probably calima.