Mosfellsbær Weather in September

Mosfellsbær in September sees moderate temperatures, with highs around 12°C (54°F) and overnight lows of 6°C (43°F). Rainfall is fairly high at around 149 mm (5.9 in) on average, so pack waterproofs just in case.

Rainfall in Mosfellsbær in September

Analyzing past climate data, one can expect approximately 18 days of rain, averaging 149 mm (5.9 in). Expect frequent rainfall this month, and not just light drizzle. When it rains, it tends to come down hard.

Temperature in Mosfellsbær in September

September in Mosfellsbær sees highs of 12°C (54°F) and lows of 6°C (43°F) overnight. Temperatures can feel cooler in the morning and evening, so layering is often the best approach. Nights drop to 6°C (43°F). Cold nights like these are actually great for sleeping well, as long as you have a warm enough duvet.

Sunshine in Mosfellsbær in September

The area enjoys a balanced 121 hours of sunlight, ensuring it's neither too overcast nor too sunny.

Wind Speed in Mosfellsbær in September

Wind speeds average 5 m/s (10 knots) during September. At this speed, gentle to moderate breezes make small trees sway and the wind creates whitecaps on water bodies. Daily variations range from moderate winds to stronger breezes, creating excellent conditions for sailing, kite flying and wind sports.

Average water temperature in September

With water temperatures around 10°C (50°F), swimming isn't really an option for most visitors. The cold sets in quickly and a wetsuit won't fully solve it.

If you prefer dry days with pleasant temperatures, September may not be the ideal month to visit Mosfellsbær. Our weather planner can help you explore destinations with more pleasant weather conditions.

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Check the conditions for any month of the year.

• January
• February
• March
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• May
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• August

• September
• October
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• December

For a detailed overview over the year and the best time to visit Iceland, check out our Mosfellsbær's climate page.

Mosfellsbær Temperature in September

Min Temperature 6°C (43°F)  

Max Temperature 12°C (54°F)  

Water Temperature 10°C (50°F) *  

Chance of Rain 60%  

Precipitation 149 mm (5.9 in)  

Rainy days 18 days  

Humidity 79% *  

Windspeed 5 m/s (10 knots) *  

Sunshine 121 hours *  

Percentage Sunshine 30% *  

* Data from: Reykjavík, Iceland (10 KM, 6 Miles).

Daily Historical Temperatures

50-year average (1976-2025)

Based on our historical records, temperatures in Mosfellsbær typically stay consistent throughout September, with daily highs averaging around 12°C (54°F). Nights are cold, with lows typically ranging from 4°C (39°F) to 8°C (46°F).

Average temperatures in September

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Daily Historical Precipitation

50-year average (1976-2025)

Average daily rainfall for each day of the month based on long-term records.

Average precipitation in September

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Historical weather for Mosfellsbær in September

Browse day-by-day weather records for Mosfellsbær spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.

Historical weather Temperatures Precipitation

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Mosfellsbær historical weather extremes in September

Based on weather observations in Mosfellsbær between 1976 and 2025, these are the recorded extremes during September.

• The warmest day in September was on September 1, 2006, with a maximum of 18°C (64°F).
• The lowest daytime temperature in September was 3°C (37°F), recorded on September 30, 1981.
• The lowest overnight temperature recorded in September was -3°C (27°F) (September 25, 2005).
• The wettest day in September Mosfellsbær was on September 12, 2007 with 36 mm (1.4 in) of precipitation.

What to Wear in Mosfellsbær in September

The weather can be unpredictable in September, so pack clothes you can easily mix and match. You could bring jeans, other long pants, and a few t-shirts. A light jacket or light sweater will be pleasant for the cooler moments. High rain levels are expected, so pack waterproof gear and an umbrella or poncho. With water temperatures around 10°C (50°F), the water is quite cold for swimming. You can skip the swimwear unless you're particularly tough. Bring sunglasses since you'll have some sunny periods throughout the month

What To Do in Mosfellsbær in September

We rated the following activities from 1 (least suitable) to 10 (best) to do.

Swimming

5/10

Cycling

5/10

Walking

5/10

Camping

3/10

Outdoor sports

5/10

Select a Month

Check the conditions for any month of the year.

• January
• February
• March
• April

• May
• June
• July
• August

• September
• October
• November
• December

For a detailed overview over the year and the best time to visit Iceland, check out our Mosfellsbær's climate page.

More climate data for Mosfellsbær

Temperature Rainfall Sunshine Humidity Wind Speed Water Temp

See the full Mosfellsbær climate overview or explore weather in Iceland.