Portland weather in May: Portland, Maine: normal highs, lows, rain and records for May
Portland in May has a normal high of 64°F and a normal low of 46°F, a daily mean of 55°F, rising from 60°F on the 1st to 69°F by the 31st. Measurable precipitation falls on 13 days in a normal May, 3.67 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 18°C and low of 8°C, 93 mm of precipitation in May.
- NOAA stationPortland International Jetport
- Station IDUSW00014764
- Location43.65°N 70.30°W
- Elevation45 ft (14 m)
- From the center6 miles
- Population69,568
- Jan 32° 16°
- Feb 35° 17°
- Mar 42° 26°
- Apr 54° 35°
- May 64° 46°
- Jun 74° 55°
- Jul 80° 61°
- Aug 79° 60°
- Sep 71° 52°
- Oct 60° 41°
- Nov 48° 32°
- Dec 38° 22°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Portland in May?
The normal high is 64°F and the normal low 46°F, for a daily mean of 54.9°F. May is 10.3°F warmer than April and 9.4°F cooler than June. May is the 5th warmest month of the year in Portland and the 8th wettest. Across the month the normal high rises 9°F, from 60°F on May 1 to 69°F on May 31. From one year to the next May's mean temperature typically moves about 2.2°F either way (NOAA's standard deviation), so roughly two Mays in three average between 53°F and 57°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 40%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| May 1 | 60°F | 41°F | 39% | 24% |
| May 8 | 62°F | 43°F | 40% | 24% |
| May 15 | 64°F | 45°F | 40% | 24% |
| May 22 | 66°F | 47°F | 40% | 23% |
| May 31 | 69°F | 50°F | 39% | 23% |
Every day of May: normal high, low and chance of precipitation (warmest afternoon May 31, coldest night May 1)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| May 1 | 60°F | 41°F | 39% | 24% | 14 h 10 min |
| May 2 | 60°F | 41°F | 39% | 24% | 14 h 10 min |
| May 3 | 61°F | 41°F | 39% | 24% | 14 h 10 min |
| May 4 | 61°F | 42°F | 39% | 24% | 14 h 10 min |
| May 5 | 61°F | 42°F | 40% | 24% | 14 h 20 min |
| May 6 | 61°F | 42°F | 40% | 24% | 14 h 20 min |
| May 7 | 62°F | 43°F | 40% | 24% | 14 h 20 min |
| May 8 | 62°F | 43°F | 40% | 24% | 14 h 20 min |
| May 9 | 62°F | 43°F | 40% | 24% | 14 h 30 min |
| May 10 | 63°F | 44°F | 40% | 24% | 14 h 30 min |
| May 11 | 63°F | 44°F | 40% | 24% | 14 h 30 min |
| May 12 | 63°F | 44°F | 40% | 24% | 14 h 30 min |
| May 13 | 63°F | 45°F | 40% | 24% | 14 h 40 min |
| May 14 | 64°F | 45°F | 40% | 24% | 14 h 40 min |
| May 15 | 64°F | 45°F | 40% | 24% | 14 h 40 min |
| May 16 | 64°F | 46°F | 40% | 24% | 14 h 40 min |
| May 17 | 65°F | 46°F | 40% | 24% | 14 h 50 min |
| May 18 | 65°F | 46°F | 40% | 23% | 14 h 50 min |
| May 19 | 65°F | 47°F | 40% | 23% | 14 h 50 min |
| May 20 | 65°F | 47°F | 40% | 23% | 14 h 50 min |
| May 21 | 66°F | 47°F | 40% | 23% | 14 h 50 min |
| May 22 | 66°F | 47°F | 40% | 23% | 15 h |
| May 23 | 66°F | 48°F | 40% | 23% | 15 h |
| May 24 | 66°F | 48°F | 40% | 23% | 15 h |
| May 25 | 67°F | 48°F | 40% | 23% | 15 h |
| May 26 | 67°F | 49°F | 40% | 23% | 15 h |
| May 27 | 67°F | 49°F | 40% | 23% | 15 h |
| May 28 | 68°F | 49°F | 40% | 23% | 15 h 10 min |
| May 29 | 68°F | 50°F | 40% | 23% | 15 h 10 min |
| May 30 | 68°F | 50°F | 40% | 23% | 15 h 10 min |
| May 31 | 69°F | 50°F | 39% | 23% | 15 h 10 min |
- Normal high
- 64°FMay average
- Normal low
- 46°FMay average
- Precipitation
- 3.67 inmonth total
- Days with precipitation
- 130.01 inch or more
- Nights at 32°F or colder
- 1
- Daylight
- 14 h 10 min to 15 h 10 minMay 1 to May 31
- Days at 70°F or more
- 7
- Days at 80°F or more
- 2
- Sunshine
- 69%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00014764; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Portland in May?
On a given May day the chance of 0.01 inch or more is 40% on average, highest around May 13 (40%). In all, 3.67 in falls on 13 days of a normal May, 1 of them with an inch or more.
In a normal May in Portland, 1 nights fall to freezing.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00014764.
How humid and windy is Portland in May?
At 3 p.m. the normal temperature is 65°F with 60% relative humidity and a dew point of 50°F; at 6 a.m. it is 55°F with 83% humidity. The wind averages 7.5 mph, most often from the south in the afternoon.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 55°F | 50°F | 83% | 5.7 mph | – |
| 9 a.m. | 62°F | 50°F | 66% | 8.5 mph | – |
| noon | 65°F | 50°F | 59% | 10.7 mph | – |
| 3 p.m. | 65°F | 50°F | 60% | 11.1 mph | – |
| 6 p.m. | 61°F | 49°F | 65% | 8.7 mph | – |
| 9 p.m. | 57°F | 50°F | 77% | 5.5 mph | 54% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014764. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for May in Portland?
The warmest May temperature on Portland's official record (since 1874) is 96°F, on May 31, 1937; the coldest is 23°F, on May 9, 1956. The wettest May brought 12.34 in (2006); the snowiest, 7.0 inches (1945).
The May mean against the 1991-2020 normal of 54.9°F: 2021 55.9°F (+1.0), 2022 55.7°F (+0.8), 2023 55.0°F (+0.1), 2024 56.0°F (+1.1), 2025 54.3°F (−0.6), 2026 55.5°F (+0.6). 5 of 6 ran warmer than normal.
| May | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 55.9°F | +1.0°F | 2.27 in |
| 2022 | 55.7°F | +0.8°F | 1.12 in |
| 2023 | 55.0°F | +0.1°F | 3.94 in |
| 2024 | 56.0°F | +1.1°F | 1.70 in |
| 2025 | 54.3°F | −0.6°F | 6.61 in |
| 2026 | 55.5°F | +0.6°F | 7.02 in |
Source: records: ACIS, NWS threaded record PWMthr; recent months: ACIS, station USW00014764. Records and recent months use complete months only.
How does May in Portland compare across Maine?
Across the 42 places PlainClimate covers in Maine, May normal highs run from 60°F in Eastport to 68°F in Fryeburg; Portland's is 64°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.