Portland weather in May 2025

Expect daytime maximum temperatures of 18°C in Portland, Maine in May based on long-term weather averages. There are 8 hours of sunshine per day on average with 12 days with some rainfall and typically 92 mm of rainfall in the month.

  • 18°C maximum daytime temperature in May in Portland18
    18°C max day temperature
  • 8 hours of sunshine per day
  • 12 days with some rainfall in May in Portland12
    12 days with some rainfall
  • 6°C minimum night-time temperature in May in Portland6
    6°C min night temperature
  • 15 hours of daylight per day in May in Portland15
    15 hours of daylight per day
  • No heat & humidity in May in Portland0
    No heat & humidity
  • 92 mm monthly rainfall in May in Portland92
    92 mm of monthly rainfall
  • UV (maximum) index 7 (High) in May in Portland7
    7 (High) UV index
  • 8°C sea temperature in May in Portland8
    8°C sea temperature

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The May weather guide for Maine (Portland) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C / mm)  |  Imperial (°F / inches)

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How hot is it in Portland in May?

Daytime temperatures usually reach 18°C in Portland in May, falling to 6°C at night.

How sunny is it in Portland in May?

There are normally 8 hours of bright sunshine each day in Portland in May - that's 52% of daylight hours.

Is the sea cold around Portland in May?

The average sea temperature around Portland in May is 8°C.

Does it rain in Portland in May?

There are usually 12 days with some rain in Portland in May and the average monthly rainfall is 92mm.

Portland May sunrise & sunset times

Browse the sunrise and sunset times for Portland in May 2025. Select a month to view Portland sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Thursday, 1st May 2025 04:33 18:44
Friday, 16th May 2025 04:15 19:01
Saturday, 31st May 2025 04:03 19:15

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