It’s been a fairly wet summer for the UK so far, with plenty of convective thunderstorms in the south, interspersed with bands of frontal rain sweeping in from the west.
Back in May, the headlines screamed that parts of the UK had had a month’s worth of rain in one day. Which sounds like an exceptional amount of rain, but just how unusual is this kind of event?
To answer this question, Ben Harvey, a meteorologist at the University of Reading, had a look at rain-gauge measurements across the UK. Using the rain gauge at Reading University Atmospheric Observatory, he found there have been only 10 occasions since 1916 when Reading had received a month’s worth of rain in one day.
“All 10 of these events occurred during July-September, so were presumably associated with intense convective storms rather than large-scale frontal systems,” he writes.
Comparing this information with 46 other rain-gauge stations across the UK, Harvey found a wide variation. Some places hadn’t had a month’s worth of rain in a day for 30 years, while others averaged one such event roughly every decade. In Scotland, a month’s worth of rain in a day was more likely to occur in the east because the east tends to be drier than the west, making it easier for one big storm to surpass a month’s worth of rain.
Meanwhile, given that convective storms are often localised, it is likely that many torrential downpours go unmeasured. So, although not an everyday experience, a month’s worth of rain falling in a day is possibly not as rare as we might think.
