Weather in Oslo in September

Shoulder season. September sits in between. You will get good days and you will lose some. Highs average 16 °C, lows 8.3 °C, and rain falls on 13 days — nothing in the month is working against you.

September ranks 4 of 12 in Oslo: past the worst of the year but short of June, which is the month to book if the dates are open.

Rain on 13 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 16 °C days and 8.3 °C nights; the spread matters more here than any single number.

What the averages hide

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest September day reached 24.5 °C and the coldest night fell to -0.3 °C, and the wettest single day dropped 45 mm — roughly 47% 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 215 mm against 45 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 96 mm average is a reasonable planning figure, not a promise.

Wind is light at 1.3 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 87%, high enough to notice on the warm days without dominating them.

How September sits in the year

The month is on the way down: 4.3 °C cooler than August, with October dropping another 6.9 °C. The first week and the last are not the same trip.

Daylight in September

13 hours of daylight, losing 2.7 hours across the month. That is between Oslo's extremes of 18.8 and 6 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 28.8 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Busy. Popular without being frantic; book the things you care about, improvise the rest.

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

September in Oslo versus nearby

If Oslo is one option among several, the nearby comparison is worth making. Kristiansand is close enough to be a coin toss — within a degree on temperature, 2 days more rain. Gothenburg is close enough to be a coin toss — within a degree on temperature, 2 days more rain.

So: September works, with June the better month by 10 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Oslo

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