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Portsmouth Weather in September
September in Portsmouth brings high temperatures around 29°C (84°F) during the day, dropping to 26°C (79°F) at night, with quite a bit of rainfall expected, averaging around 136 mm (5.4 in) for the month.
Rainfall in Portsmouth in September
You can expect rain on around 22 days based on historical patterns, with 136 mm (5.4 in) average for the month. Expect frequent rainfall this month, and not just light drizzle. When it rains, it tends to come down hard.
Temperature in Portsmouth in September
Portsmouth in September gets highs of 29°C (84°F) during the day and drops to 26°C (79°F) at night. The days can feel warmer than the evenings, so packing for both parts of the day is a good idea. At 26°C (79°F) overnight, the heat doesn't let up much after dark. If you're staying somewhere without air conditioning, a cold shower before bed and keeping the air moving can help.
Sunshine in Portsmouth in September
With approximately 212 hours of sunshine, the days are filled with clear skies. It makes it a perfect month for being outside.September in Portsmouth has its charm, but if you're looking for destinations with pleasant temperatures and sunny skies, our weather planner can help you explore other options in the world.
Portsmouth Temperature in September
Min Temperature
26°C (79°F)
Max Temperature
29°C (84°F)
Chance of Rain
73%
Precipitation
136 mm (5.4 in)
Rainy days
22 days
Humidity
72% *
Sunshine
212 hours *
Percentage Sunshine
*
* Data from: Douglas-Charles Airport, Dominica (18 KM, 11 Miles).
Portsmouth Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Portsmouth - and find the best time to visit.
Daily Historical Temperatures
49-year average (1976-2025)
Based on our historical records, temperatures in Portsmouth typically stay consistent throughout September, with daily highs averaging around 29°C (84°F). Nights are warm, with lows around 24°C (75°F).
Average temperatures in September
Historical weather records for Portsmouth in September
Browse day-by-day weather records for Portsmouth spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Portsmouth historical weather extremes in September
The extremes listed below come from historical weather data collected in Portsmouth from 1990 through 2025.
- On September 1, 2005, temperatures climbed to 34°C (93°F), marking the warmest September day on record.
- Portsmouth experienced its chilliest September day on September 8, 1996, reaching only 25°C (77°F).
- The coldest night in September in Portsmouth was on September 8, 2023, with a minimum of 10°C (50°F).
Best Places in Dominica in September
Find out more about the weather in Dominica and which places have the best travel conditions in this month. See all of Dominica in September →
perfect weather
pleasant
tolerable
unpleasant
poor
Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C (68°F) and 29°C (84°F) and not too much precipitation (less than 90 mm (3.5 in) a month).
What to Wear in Portsmouth in September
Warm temperatures in September make for comfortable sightseeing weather. Pack breathable fabrics like cotton shirts, knee-length shorts or skirts, and comfortable walking shoes. A thin long sleeve for indoor spaces is handy. Prepare for significant rainfall with proper waterproof clothing and shoes. You'll definitely want to pack sunglasses and sunscreen. There will be plenty of bright sunshine this month.
What To Do in Portsmouth in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
-
Swimming9/10 -
Cycling7/10 -
Walking7/10 -
Camping7/10 -
Outdoor sports7/10
Portsmouth 3-Day Forecast
More climate data for Portsmouth
Temperature Rainfall Sunshine Humidity
See the full Portsmouth climate overview or explore weather in Dominica.
Popular in September
Where to go in September - average daytime high across popular destinations.
Salisbury
29°C (84°F) Scotts Head Village29°C (84°F) Roseau29°C (84°F) Marigot29°C (84°F) Portsmouth29°C (84°F) Calibishie29°C (84°F) Pont Cassé29°C (84°F) Castle Bruce
29°C (84°F) Bucket list
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