Malta gets almost no rain between May and September.
When it finally comes, usually in the second half of September, it arrives as a thunderstorm rather than as drizzle.
The ground has been baked for five months and takes almost nothing in. Whatever falls runs straight off.
Why the roads flood so fast
The island is limestone with thin soil, and the drainage was built for a smaller country.
A short heavy storm puts more water on the road than the system can take.
Low points fill first. The Msida area, parts of Marsa and the bottom of any valley road are the usual ones.
They go from dry to axle deep in fifteen minutes.
It also clears fast. An hour after the rain stops most of it has drained away.
Driving in it
The first rain lifts five months of oil and dust off the surface. It is the most slippery day of the year.
Do not drive into standing water in a valley. You cannot see how deep it is and the current can move a car.
Traffic seizes up completely. Add an hour to anything.
Give the scooters and motorcycles room. They come off on the first wet day more than any other.
On the water
Storms come with sudden wind changes.
The Gozo ferry and boat trips are cancelled at short notice, and the Comino boats stop first.
If you have a crossing booked, check the morning of rather than the day before. There is more on the four winds and what each does.
Swimming in the day or two after a storm is worth avoiding at bays fed by a valley. Runoff carries whatever was on the road into the sea.
If you live here
Clear the roof drains before the second half of September. A blocked one puts the water inside rather than outside.
Flat roofs and the shafts between buildings are where it gets in. Most Maltese leaks start at a roof outlet, not a wall.
Power cuts are short but common during the first storms.
What the rain is good for
The island turns green within about two weeks.
The countryside that looks dead all summer comes back, and the walking from October onwards is the best of the year.
The valleys run briefly, which is the only time you will see moving fresh water in Malta.
Wied il-Lunżjata in Gozo and the valley below Baħrija are the two that show it best.
