Portsmouth — Water Temperature in May
Water Temperature Range
48°F
minimum
53°F
average
59°F
maximum
Water Temperature Chart for Month
The chart shows the average daily water temperature for each day of the month based on historical data.
Table of Water Temperatures by Day of the Month for Previous Years
| Day | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| MAY 1 | 50°F | 52°F | 48°F | 50°F |
| MAY 2 | 50°F | 52°F | 48°F | 50°F |
| MAY 3 | 52°F | 52°F | 48°F | 52°F |
| MAY 4 | 52°F | 52°F | 48°F | 52°F |
| MAY 5 | 52°F | 52°F | 50°F | 52°F |
| MAY 6 | 52°F | 54°F | 50°F | 52°F |
| MAY 7 | 52°F | 54°F | 48°F | 52°F |
| MAY 8 | 54°F | 54°F | 50°F | 52°F |
| MAY 9 | 52°F | 54°F | 50°F | 52°F |
| MAY 10 | 52°F | 52°F | 50°F | 52°F |
| MAY 11 | 52°F | 54°F | 50°F | 52°F |
| MAY 12 | 54°F | 54°F | 50°F | 52°F |
| MAY 13 | 52°F | 54°F | 50°F | 52°F |
| MAY 14 | 54°F | 54°F | 52°F | 52°F |
| MAY 15 | 54°F | 54°F | 54°F | 52°F |
| MAY 16 | 54°F | 55°F | 50°F | 52°F |
| MAY 17 | 54°F | 57°F | 52°F | 52°F |
| MAY 18 | 54°F | 55°F | 52°F | 54°F |
| MAY 19 | 54°F | 55°F | 52°F | 54°F |
| MAY 20 | 54°F | 54°F | 52°F | 54°F |
| MAY 21 | 54°F | 55°F | 52°F | 54°F |
| MAY 22 | 55°F | 57°F | 52°F | 54°F |
| MAY 23 | 55°F | 57°F | 52°F | 54°F |
| MAY 24 | 54°F | 55°F | 52°F | 54°F |
| MAY 25 | 54°F | 55°F | 52°F | 54°F |
| MAY 26 | 54°F | 55°F | 52°F | 54°F |
| MAY 27 | 54°F | 57°F | 52°F | 54°F |
| MAY 28 | 55°F | 57°F | 54°F | 54°F |
| MAY 29 | 54°F | 55°F | 54°F | 55°F |
| MAY 30 | 54°F | 55°F | 54°F | 54°F |
| MAY 31 | 55°F | 57°F | 54°F | 55°F |
May: Climate and Swimming Opportunities
Average Night Air Temperature
48°F
Average Day Air Temperature
61°F
Precipitation Amount per Month
1.30 in
Number of Rainy Days
10
Daylight per Day
15 hrs
Sunshine per Day
7 hrs
Average Wind Speed
11 mph
Average Humidity
80%
With such a ratio between the average monthly temperatures of water and air, swimming feels very cold and is only for cold-water enthusiasts. Most people will prefer just a brief splash, because warming up afterward can take time.