מזג האוויר בפורטלנד במרץ

Regulars sum up this month with a local saying rather than a forecast: if you don't like the weather, wait five minutes - a morning can start rainy and cold and end sunny and warm, sometimes needing a rain jacket, a fleece and short sleeves all within the same day. Our row backs the mild, changeable average, 20.8C over 10.3C nights, with 50.2mm of rain across 8.3 days. Regulars are consistent that genuinely settled, predictable weather doesn't really arrive until early July, so layering isn't just advice for this month specifically - it's the baseline strategy through the whole spring stretch. The record: humidity 70 percent, 10.8 hours of sun, an 11.9 kph wind and one of the cleanest air readings in this project, AQI 34.

Nobody on this board will predict an August here, and the variable they mean is not rain but smoke. Fires in central Oregon, eastern Washington or British Columbia can send it down the Cascades and through the Gorge into the city, and whether it arrives depends entirely on which way the wind is sitting that week; the standing advice is to have a plan B. Our AQI of 34 is a thirty-year normal and cannot see a smoke week, which is exactly why the board's warning is worth more than the column. The weather otherwise is the best of the year: 28.1C over 15.8C, 7.7mm of rain across 1.4 days, 11.8 hours of sun. The record: humidity 57 percent and an 11.6 kph wind.

The local joke here is a date: summer begins on the 5th of July, because it can stay cool and showery right up to the 4th and then simply stops raining until late September. Our row is the joke in numbers - 4.5mm across 1.2 days, which is as close to a dry month as this collection holds outside the deserts. July is also the warmest, 27.6C over 15C, with the occasional run at the upper thirties. Twelve degrees between day and night and only 57 percent humidity mean the evenings are genuinely cool, and 13.1 hours of sun sit inside 15.3 of daylight. The record: a dew point of 11.5C, a 12.3 kph wind and AQI 29, among the cleanest air we hold for a large city.

September is the month long-time Oregonians name as the best of the year: sunny, dry, neither too hot nor too cold, with the least rain of the year falling between July and September. It is also when people schedule outdoor weddings, for the odds. The one risk is smoke - wildfire smoke is likelier in September than in July, unpredictable when it comes, easing later in the month, and less of a problem at the coast than inland. Our row is the dry half of that picture: 46.4mm across 5.4 days. The record: 23.9C days, 13.5C nights, humidity 67 percent and 9.8 hours of sun.