シアトルの月別の天気

The stereotype of Seattle weather is that it is Rain City, where the sky is always grey, rainy, and depressing. Despite the reputation, the main challenge of Seattle's weather is more the overcast skies than the rain, and in fact Seattle has less annual rainfall than most cities east of the Rocky Mountains. Seattle's rain usually comes in a drizzle that lingers for days, which only occasionally strengthens to a full-blown torrent that rarely lasts long. Many residents call this period of overcast "the season of grey" as it lasts from late October to early March every year. The season is also accompanied by the short daylight hours of the winter, where its only light out from 7:45AM to 4:30PM. It may surprise you that rain is virtually absent from July through September, making Seattle an excellent place to spend summer. It's warm and comfortable a decent amount of the time, with little to moderate humidity, with average summer highs of and lows of .…

Regulars are precise about January and want you to stop worrying about the rain: "historical rain in January is a little over 5 inches spread out over 18 days" — roughly a third of an inch a day, "mostly a drizzle." It does not rain daily and it does not rain all day; some Januaries deliver glorious sunny cold ones. It also rarely falls below freezing or snows. What they say actually gets to people is the light: "it gets dark here at 4:15pm on our shortest days," about 8.75 hours between an 8am sunrise and a 4:45pm sunset, and the most-disliked thing about the month isn't the weather but that "the days are so very short." Our record has 8.9 daylight hours, 19 rain days and 8°C days — the numbers say the same thing the forum does.

Seattle forum threads describe February as genuinely mixed - some stretches bring drizzly, overcast, grey days typical of the region's wet season (which runs roughly mid-October through April), while other years bring a welcome week or so of milder, lighter-sun weather that winter-weary locals specifically look forward to. Snow chances were described as relatively low by this point in winter, with January and early February the more likely window for any accumulation. One consistent tip from posters familiar with the wider region: the northern Olympic Peninsula tends to run drier and sunnier than Seattle proper in February, a worthwhile alternative for anyone chasing better odds of sun.

Regulars describe this as the most variable month of the year here, unlike the more settled fall and winter, with two genuinely distinct outcomes possible on any given day - sunny and into the low 70s Fahrenheit, or overcast with highs stuck in the upper 50s to low 60s. Our row backs the mild, changeable average across that range, 19.1C over 9.5C nights, with 34mm of rain across 5.3 days. Regulars are consistent this is still a genuinely good time to visit, flowers in full bloom and springlike energy throughout the city, with layering the standard advice given how unpredictable a specific day can turn out. The record: humidity 74 percent, 10.8 hours of sun, a 12.6 kph wind and AQI 44.

Juneuary is the local word for the version of this month that feels like January, and the local claim is that summer does not start until the 5th of July - the same joke the Portland board tells, two hundred kilometres south. The instruction that follows is precise: the 30th of June is a different month from the 1st, so come at the end. Our row is kinder than the nickname. Rain is 29.5mm across 5.1 days, and there are 11.6 hours of sun inside 15.9 of daylight, so the grey is brief showers between sun breaks rather than a ceiling. What June lacks is warmth - 21.6C by day, 12C at night. The record: humidity 71 percent, a 12.5 kph wind and AQI 39.

Seattle's reputation for rain simply doesn't apply in July, and the forum is emphatic about it: the dry, sunny stretch runs from around mid-June into October, with July and August the warmest and least wet months of the year. Regulars pin the switch to roughly 8 July, after which reliably warm, sunny weather sets in, and single out the last week of July and first week of August as the best of it. The real averages back them up — highs around 25°C and rain on only about four days in the whole month.

Seattle-forum threads on August are almost giddy about the weather - this and the two months around it are the reliably dry, sunny stretch of the year, with posters calling a soggy day genuinely rare and temperatures running warm without the humidity that makes other cities miserable in summer. The one recurring caveat has nothing to do with rainfall: more than one thread flags wildfire smoke as the real risk, a haze that can roll in and ruin an otherwise perfect week with no warning. Cruise-ship crowds pack Pike Place Market and the Space Needle on port days. The record backs the dry read completely: 25.2C days, 14.7C nights, just 12mm total across 1.6 days, 11.4 hours of sun and an AQI of 44 - though that AQI can spike hard on a bad smoke day, which the average doesn't show.

Regulars call this one of the city's best-looking months on paper, and are specific about why: the rains that define this region typically hold off until mid-October, and the first week of the month is often the driest and warmest stretch, with the back half cooling off a little as it goes. Our row backs the shift, 21.4C over 12.3C nights, with 35.5mm of rain across 5.6 days - a real total, but light next to what regulars describe arriving a month later. Evenings call for a light jacket or sweatshirt once the sun goes down. The one caveat some years bring is wildfire smoke drifting in from regional fires, not present every September but enough that regulars mention checking air quality before a trip built around outdoor views. The record: 9.5 hours of sun, a 12.3 kph wind and AQI 40.