Portsmouth — Water Temperature in September
Water Temperature Range
72°F
minimum
77°F
average
84°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 |
|---|---|---|---|---|
| SEP 1 | 81°F | 79°F | 84°F | 82°F |
| SEP 2 | 79°F | 77°F | 82°F | 81°F |
| SEP 3 | 79°F | 77°F | 81°F | 82°F |
| SEP 4 | 79°F | 77°F | 79°F | 81°F |
| SEP 5 | 79°F | 77°F | 81°F | 82°F |
| SEP 6 | 79°F | 75°F | 79°F | 84°F |
| SEP 7 | 79°F | 77°F | 79°F | 82°F |
| SEP 8 | 79°F | 77°F | 79°F | 82°F |
| SEP 9 | 79°F | 77°F | 79°F | 82°F |
| SEP 10 | 79°F | 77°F | 79°F | 82°F |
| SEP 11 | 77°F | 75°F | 79°F | 81°F |
| SEP 12 | 77°F | 75°F | 77°F | 81°F |
| SEP 13 | 77°F | 73°F | 77°F | 81°F |
| SEP 14 | 77°F | 73°F | 77°F | 82°F |
| SEP 15 | 77°F | 73°F | 77°F | 81°F |
| SEP 16 | 77°F | 72°F | 77°F | 81°F |
| SEP 17 | 77°F | 73°F | 79°F | 81°F |
| SEP 18 | 77°F | 72°F | 77°F | 81°F |
| SEP 19 | 77°F | 73°F | 81°F | 79°F |
| SEP 20 | 77°F | 70°F | 79°F | 81°F |
| SEP 21 | 75°F | 72°F | 77°F | 77°F |
| SEP 22 | 75°F | 72°F | 77°F | 79°F |
| SEP 23 | 75°F | 73°F | 77°F | 75°F |
| SEP 24 | 75°F | 72°F | 77°F | 77°F |
| SEP 25 | 75°F | 72°F | 77°F | 73°F |
| SEP 26 | 75°F | 73°F | 77°F | 73°F |
| SEP 27 | 75°F | 75°F | 77°F | 72°F |
| SEP 28 | 75°F | 75°F | 75°F | 72°F |
| SEP 29 | 75°F | 75°F | 77°F | 73°F |
| SEP 30 | 73°F | 73°F | 75°F | 73°F |
September: Climate and Swimming Opportunities
Average Night Air Temperature
64°F
Average Day Air Temperature
77°F
Precipitation Amount per Month
2.84 in
Number of Rainy Days
9
Daylight per Day
12 hrs
Sunshine per Day
8 hrs
Average Wind Speed
9 mph
Average Humidity
76%
At such water and air temperatures, swimming feels truly comfortable and relaxing. The warm water won’t cool you down, so you can stay in for a long time without getting chilled.