Thirty years of rain, in numbers

A normal August in London brings 59.5mm. One brought 0.9mm.

An average is a poor guide to a month you have to garden through. Across the whole list, 709 town-months have at some point delivered under 5mm — near enough nothing at all.

In Britain alone there are 48 of them. These are the driest single months on the British part of the list, and the middle column is what one of those months is supposed to bring.

And where the fall is furthest

Across the whole list the startling ones are different: places whose normal month brings two hundred millimetres and which have had one bring three.

Two tables, two sorts, and the difference is the point. Within Britain the shock is how little fell, so it ranks on that. Across the world it has to rank on the gap instead — sorted by the smaller figure, the list fills with Perth, Adelaide and Darwin, where a rainless month is simply what summer is and nothing is being revealed.

From 131mm a year to over 2,000mm

^† Vancouver reads high — the North Shore mountains sit in the same 11km cell as the city, so the figure is the cell's rainfall rather than the town's. It is left in the ranking rather than quietly dropped, because a wettest-places table with the wettest place removed would be the less honest page.

The same month, thirty years apart

These are the single calendar months that have varied most between their driest year and their wettest. A figure with this much room around it is not something anyone can plan by, which is the honest argument against gardening by the average.

Some places have a rainy season. Some barely have a calendar.

A town's wettest month divided by its driest. It says nothing about how wet a place is — only about how much the time of year decides.

Only 63.5% of rainy days give a garden anything

Counted with the same arithmetic the daily answer uses: a day only counts if enough fell to get past the leaves and the soil surface. Across 201 towns the typical figure is 63.5% — which means roughly half of the days it rains, nothing reaches a root. These are the places where that gap is widest.

Where these come from

Daily rainfall for every town, 1995 to 2024, totalled by calendar month and then averaged across the thirty years. The reanalysis grid is about eleven kilometres across, so a town shares its cell with whatever else is in it — which is worth knowing before quoting any single figure here as a fact about a street.

How the daily answers are worked out · Every town we answer for