When is it actually a storm — and what does that mean for your roof?
A wind gust warning is not the same as a storm. The difference is in the numbers, and those numbers are about your roof tiles.
"It's going to storm" means something different in everyday speech than in meteorology, and for a roof that difference matters. What causes damage is rarely the hourly average the official storm definition rests on, but the individual gust in between.
Dutch meteorological institute KNMI describes wind gusts as brief squalls or gusts of at least 50 kilometres per hour. From 75 kilometres per hour KNMI speaks of severe gusts, and gusts over 100 kilometres per hour are called very severe gusts. The official storm sits alongside that: KNMI speaks of a storm from wind force 9, precisely when the average wind speed equals wind force 9 for at least 1 hour.
That holds the practical lesson. A day without an official storm can still deliver severe gusts, and one such gust under a loose tile or a curled roof edge is enough. So when a warning comes, look at the gust figures quoted rather than the word storm — that is the number concerning your roof covering.
Then the calendar: KNMI notes that the storm season begins in September and that the first storm often arrives in November. That makes late August the moment to look, not October. If something already looks loose or porous, having roof tiles replaced (€ 125-350) before the season is cheaper than an emergency repair (€ 150-450) during the first wet week; every guide rate is in the price index.