London Is Drier Than Seattle. July Tells the Opposite Story.

Choose July and London is the wetter city. Choose November and Seattle receives more than twice as much precipitation. Add the whole year and Seattle wins comfortably. All three statements come from the same climate comparison.

That is the problem with giving a city one permanent rain rating. London and Seattle are both plausible places to picture a wet pavement beneath a gray sky. But Seattle concentrates much more of its water in the cool half of the year, while London keeps a more even supply across the calendar. A summer visitor and a winter resident can describe the same city very differently without either being mistaken.

The Annual Winner Loses in July

Use the same thirty years: 1991-2020. Heathrow is our London-area station and Seattle-Tacoma International Airport is our Seattle-area station. The comparison measures precipitation depth, including the liquid equivalent of frozen precipitation in NOAA's records. One inch equals 25.4 millimeters.

Sources: Met Office, Heathrow; NOAA, station USW00024233. Metropolitan reference stations, not neighborhood-wide measurements.

Seattle's annual total is about 62% higher. Yet Heathrow's July total is about three times Sea-Tac's. The larger annual number does not mean that every season is wetter, any more than a larger annual heating bill means every month is colder.

The reversal changes the practical meaning of summer. In Seattle, July belongs to a pronounced dry interval. In London, it is a brighter, warmer part of a year that still distributes rainfall through every month. Neither normal promises a dry wedding or picnic, but the calendars offer different starting odds for outdoor plans.

Seattle Has a Wet Half and a Dry Half

Summing October through March gives about 75% of Sea-Tac's annual precipitation, against about 54% at Heathrow. Those are calculations from the published monthly normals, not a new weather forecast. They reveal the central contrast more clearly than the annual totals do.

The National Weather Service's Seattle climate account describes a northward summer storm track and a wetter, cloudier cool season. Seattle's dry summer is not a lucky interruption in an otherwise uniform drizzle. It belongs to the region's atmospheric cycle.

This is also why a single memorable week is an unreliable introduction. Visiting Seattle in July and deciding its wet reputation is absurd misses the months that generate most of the water. Visiting in November and assuming that summer is simply a warmer version misses the opposite half of the story.

London asks for a less dramatic seasonal adjustment in rainfall. Heathrow's wettest monthly normal is November; its driest is March. Even the driest month averages nearly 39 millimeters. There is no equivalent to Sea-Tac's 15-millimeter July at this London station.

A Rainy Day Is Not a Unit of Time

Depth still leaves out how rain interrupts a day. Heathrow averages 111.66 days a year with at least one millimeter. Sea-Tac's commonly quoted measurable-precipitation count uses a lower threshold: 0.01 inch, or 0.254 millimeter. Putting those totals in adjacent columns as though “rain day” meant the same thing would manufacture precision.

Even an identical threshold would not distinguish a brief shower from hours of light rain. Nor would it tell you whether the shower arrived during the school run or overnight. A daily count records that enough water fell, not how much of your day it occupied.

The regional scenery can make that distinction harder to remember. Waterfalls, wet forest, and mountain cloud all belong to the Seattle-area imagination, but they are not a reading from a downtown rain gauge. The Olympics and Cascades create strong variations across the region. A trip into the surrounding landscape is a different weather sample from a day in the city.

The Drier City Has the Shorter Winter Day

London also sits farther north. On December 21, 2026, its sunrise-to-sunset interval is about 7 hours 50 minutes; Seattle's is about 8 hours 25 minutes. In June the relationship reverses: on June 21, London gets about 16 hours 38 minutes, Seattle about 15 hours 59 minutes. These are astronomical daylight windows, not measured sunshine.

Less annual rain therefore does not buy London a longer winter afternoon. For a person whose free time starts after work, the combination of cloud and a short daylight window may matter more than the water volume. For someone mainly imagining summer weekends, Seattle's seasonal dry spell may be the more important distinction.

London and Seattle are not competing for a single title of “rainier.” London receives less water over the year and spreads it more evenly. Seattle puts much more into the cool season, then offers a substantially drier July. The useful question is which part of the year you are picturing when you say you dislike rain.