Last updated: June 24, 2025
In Portland, United States, the average temperature in May hovers around 21°C (70°F). During this time, expect a minimum of 4°C (39°F) and soaring to a maximum of 33°C (92°F). With an average humidity of 82%, you might feel the warmth even more. Be prepared for some rain, as 122 mm (4.8 in) of precipitation typically falls over 13 days.
In May in Portland, the average temperature is 21°C (70°F). The maximum can reach 33°C (92°F), while the minimum can dip as low as 4°C (39°F). This weather makes Portland an ideal destination for travelers seeking mild temperatures and a range of outdoor activities.
In Portland in May, the precipitation amount is 122 mm (4.8 in) recorded over a span of 13 days.
In Portland in May, humidity is 82%. With an average temperature of 21°C (70°F), this humidity feels like a warm, sticky embrace that can quickly lead to discomfort for travelers, making outdoor activities less enjoyable and requiring frequent breaks for hydration.
In Portland in May, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Portland.
UV Risk Categories
Weather in Portland varies notably across the year, with each month offering distinct climate conditions. This page compares May’s weather to other months in Portland, focusing on differences in temperature, rainfall, humidity, and UV levels.
Temperature | Precipitation | Humidity | UV | |
---|---|---|---|---|
January Weather | 4°C (40°F) | 105 mm (4.1 inches) | 87% | moderate |
February Weather | 7°C (44°F) | 185 mm (7.3 inches) | 86% | high |
March Weather | 11°C (52°F) | 157 mm (6.2 inches) | 86% | high |
April Weather | 15°C (59°F) | 150 mm (5.9 inches) | 82% | very high |
May Weather | 21°C (70°F) | 122 mm (4.8 inches) | 82% | very high |
June Weather | 25°C (77°F) | 141 mm (5.5 inches) | 83% | extreme |
July Weather | 27°C (80°F) | 125 mm (4.9 inches) | 80% | extreme |
August Weather | 25°C (78°F) | 124 mm (4.9 inches) | 74% | very high |
September Weather | 23°C (74°F) | 125 mm (4.9 inches) | 71% | very high |
October Weather | 17°C (63°F) | 138 mm (5.4 inches) | 78% | high |
November Weather | 9°C (48°F) | 88 mm (3.4 inches) | 88% | moderate |
December Weather | 7°C (45°F) | 147 mm (5.8 inches) | 88% | moderate |