Weather in Portland in May

A good month. May works. It is not the peak, but nothing about it fights you. Highs average 19.2 °C, lows 8.7 °C, and rain falls on 13 days — nothing in the month is working against you.

May ranks 5 of 12 in Portland: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain on 13 days, 2 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest May day reached 35.5 °C and the coldest night fell to 2.1 °C, and the wettest single day dropped 35 mm — roughly 44% of the month's rain in one day.

May is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest May on record still delivered 146 mm against 15 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 79 mm average is a reasonable planning figure, not a promise.

Wind is light at 2.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 82%, high enough to notice on the warm days without dominating them.

How May sits in the year

The month is on the way up: 4.2 °C warmer than April, and June adds another 3 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short.

Daylight in May

14.9 hours of daylight, gaining 1.2 hours across the month. That is between Portland's extremes of 15.7 and 8.7 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 27.7 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Busy. Popular without being frantic; book the things you care about, improvise the rest.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

May in Portland versus nearby

If Portland is one option among several, the nearby comparison is worth making. Eugene is close enough to be a coin toss — within a degree on temperature, 1 day less rain. Seattle is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

So: May works, with July the better month by 15 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Portland

See all twelve months in Portland, or where else to go in May.