September weather forecast
Longyearbyen, Svalbard and Jan Mayen

With September setting in, the cheerful chatter of birds gradually subsides and the advent of winter looms again. The temperature drops drastically to 1°C (33.8°F), taking a steeper descent compared to the previous month’s 6°C (42.8°F). Longyearbyen’s day fades away much earlier as daylight hours slump to 14.5, marking the sun's retreat. This month becomes a stark contrast where the snow covers the ground for 11 days after a summer of near absence. The plummeting temperature and returning snowfalls are formidable indications of September's weather change.

Temperature

The onset of September entails a temperature shift, as the average high-temperature decreases from a chilly 6°C (42.8°F) in August to an icy 1°C (33.8°F). Consistently, Longyearbyen reports average nighttime temperatures of -3°C (26.6°F) during September, a marginal step down from its daytime highs.

Rainfall

In September, in Longyearbyen, the rain falls for 14 days. Throughout September, 25mm (0.98") of precipitation is accumulated. In Longyearbyen, Svalbard and Jan Mayen, during the entire year, the rain falls for 86 days and collects up to 271mm (10.67") of precipitation.

Snowfall

Months with snowfall in Longyearbyen are January through December. In September, snow falls for 11 days. In Longyearbyen, during the entire year, snow falls for 176 days.

Sea temperature

In Longyearbyen, the average seawater temperature in September is 5°C (41°F).
Note: Caution: 5°C (41°F) temperatures below 10°C (50°F) during swimming can result in intense cold shock and quickened breathing.

Daylight

With an average of 14h and 30min of daylight, September has the longest days of the year.
On the first day of the month, sunrise is at 03:43 and sunset at 22:10. On the last day of September, in Longyearbyen, sunrise is at 07:30 and sunset at 18:04 CEST.

Sunshine

In September, the average sunshine in Longyearbyen is 2.5h.

UV index

In September, the average daily maximum UV index in Longyearbyen is 1. A UV Index of 2, and less, symbolizes a minimal health hazard from exposure to the Sun's UV rays for average individuals.
Note: In September, an average UV index of 1 transforms into the following instructions:
While most can endure approximately an hour in the sun without burning, children always require protection from sunlight. Avoiding direct sun during mid-day hours can prevent harmful UV radiation exposure. In the presence of strong sunlight, it's crucial to wear sunglasses that ward off UVA and UVB rays. Be alert to the fact! The reflection from snow can nearly double the UV radiation of the Sun.