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Slough sits in the Met Office's south-east and central southern England area. Each bar is one year's total; the dark line is the ten-year average, which is what a trend looks like once single wet and dry years are smoothed out; the dashed line is the 1991–2020 average of 806 mm. 2025 brought 715 mm, close to that. The wettest year here since 1996 was 2000 (1,109 mm), the driest 2005 (610 mm).
Rainfall over a whole region, not a measurement in Slough itself, and a wet year is not the same thing as a flood: what floods a river is how much falls at once and how wet the ground already was. Average rainfall: HadUK-Grid v1.3.2, Met Office. Contains public sector information licensed under the Open Government Licence v3.0.
Year by year, each figure divided by what changed about the measuring — the gauge fleet, the flood areas on the register, the overflows monitored.
Slough, Environment Agency warning archive, 2009–2025
The last 6 years average 2.42 per area, against 1.54 per area for the first 6 — 58% higher.
El Niño winter La Niña winter. Marked for context, not as a cause — these are states of the Pacific, and one wet fortnight moves a British year more than a whole season's pattern does. What El Niño and La Niña are, and what they did here.
The raw count went from 2 to 11 alerts and warnings between 2009 and 2025, while the areas warned went from 2 to 3 — which is what the chart divides by.
Raw warning counts have risen steeply since 2006, but so has the number of flood areas that can be warned at all. This chart divides by the areas actually warned, which is the part that is about the weather rather than about the register. Warning policy also changed over the period.
See all four across the whole UK, and how to read them
Rebuilt on 21 September 2026, from data banked up to the end of 2026. Only whole calendar years are counted, so 2026 will appear here once it has finished. The rebuild runs weekly.
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