May weather outlook: Warm and dry days are on the way
PORTLAND, Ore. (KOIN) — Portland is set to kick off May with an early taste of summer as temperatures soar well above seasonal norms on Thursday.
Thanks to a strong ridge of high pressure forming over the western U.S., Portland is expected to warm into the low to mid-80s under sunny skies Thursday.
Average highs for late April and early May typically hover in the mid-60s, making this a bump in temps nearly 20 degrees above normal. The heat won't last long as temperatures are expected to fall back into the mid-60s by the weekend.
May Outlook: A Mix of Spring Warmth and Dry Days
According to NOAA's Climate Prediction Center, the May 2025 outlook shows near-normal temperatures for much of northwest Oregon. That means there is no strong lean toward a warmer or cooler trend. That leaves room for a little bit of everything, like a few warm spells, cooler stretches, and all the variability that spring is known for. Areas of Southern Oregon, California, and the desert Southwest are more likely to experience above-normal heat.
When it comes to rainfall, Portland is trending slightly drier than normal with a 33–40% chance for below-normal precipitation this month. That means that showers are still likely at times, but May could end with below-average rainfall totals and plenty of dry days for outdoor plans.
Last May (2024) brought a stretch of record-breaking 90°+ heat near the middle of the month, as well as two cool and wet stretches in the 50s. In the end, rainfall landed just below average. Portland typically sees around 2.51 inches of rain in May.
The city's first 80° day of the year typically arrives around May 8, and the first 90° day comes on average by June 18.
Spring can be unpredictable. Some years bring prolonged gray skies and rain, while others jumpstart summer with surges into the 80s and 90s. Or, it's all-of-the-above, like we saw last year. Even with monthly outlooks offering guidance, it's always good to be ready for these rapid shifts.
If you're heading outdoors during this upcoming heat up, remember to stay hydrated and wear sunscreen. The UV Index in Portland has reached high levels lately, meaning sunburn can occur in as little as 15 minutes under direct sunlight.
Stay up to date with the weather forecast with the KOIN 6 Weather Team.
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