Close the windows before the dust arrives, not after

When calima dust is blowing in from the Sahara, close your windows before you leave the flat, not when you get back. It sounds trivial. It is not, because the dust is fine and gets on everything, the laptop keyboard and the balcony chairs included. I learned this on a day that looked perfectly normal, which is how calima starts. Now I check the forecast before a long day around the Rambla. A cloth over the keyboard is a good idea too.