Weather in Reykjavík in September

A hard month. September is a hard month in Reykjavík, and worth planning around. You should expect rain on 22 days of the month, which is more days wet than dry.

September ranks 5 of 12 in Reykjavík: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain on 22 of the month's 30 days, 6 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Layers, and a genuinely waterproof outer — at 10.3 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: the day barely swings — 3.9 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 16.8 °C and the coldest night fell to -0.6 °C, and the wettest single day dropped 62 mm — roughly 34% of the month's rain in one day.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 293 mm against 102 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 181 mm average is a reasonable planning figure, not a promise.

Wind is light at 9.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 88%, which at 10.3 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How September sits in the year

The month is on the way down: 3 °C cooler than August, with October dropping another 3.9 °C. The first week and the last are not the same trip. Rain has already shifted: 5 days more than August had.

Daylight in September

13.2 hours of daylight, losing 3.2 hours across the month. That is between Reykjavík's extremes of 21 and 4.3 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 10.9 °C in September — too cold to swim without a wetsuit. This is the warmest the water gets all year.

How busy it gets

Shoulder. The value months — prices ease off and you get the place closer to itself.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Reykjavík versus nearby

If Reykjavík is one option among several, the nearby comparison is worth making. Akureyri is the weaker option in September — 5.4 °C cooler, 2 days less rain. Glasgow is a better bet in September — 5.2 °C warmer, 4 days less rain.

So: September works, with July the better month by 17 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Reykjavík

See all twelve months in Reykjavík, or where else to go in September.