Weather in Kos in September

How September compares

September is the 3rd warmest month of the year in Kos and ranks 88th of 134 destinations we compare for September - see where else is hot in September. Within Greece it is 25th of 44 (Greece in September). Against London's average high of 18.6°C in September, Kos is 6.7°C warmer by day and 11.3°C warmer at night.

Daytime and night-time in September

The typical September day in Kos peaks at 25.3°C, but that is an average: the warmest 10% of days reach 27.7°C or more. About 57% of days top 25°C and 1 in 50 pass 30°C. Nights average 22.5°C; one night in ten drops to 20.4°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest September day here reached 32.8°C (2020-09-02) and the coldest night 17.8°C (2000-09-27).

Rain in September

Dry (3 rainy days or fewer): about 2 days with 1 mm or more, 15 mm in total. Year to year it varies a lot - the wettest September was 2015 with 110 mm, the driest 1991 with 0 mm. Humidity averages 72%.

Sea temperature in September

The sea averages 24.5°C - warm enough to swim (22°c+). Depending on the year it ranges from 23.4°C to 25.7°C. For the warmest sea here, come in August (25.2°C).

Sunshine and daylight

Around 11.1 hours of sunshine a day (estimated from cloud cover), 12.2 hours of daylight: the sun rises about 06:53 and sets about 19:19 local time in mid-September. Average cloud cover is 9%.

Is September a good time to visit Kos?

Yes - it is one of the better months: hot days, little rain and long sunny days. The best months for Kos on our scoring are August, July, June; months averaging 25°C or more: Jul, Aug, Sep.

Warm days, with little cooling after dark

September feels appreciably warmer than home: Kos has an average daytime high of 25.3°C, compared with London's 18.6°C. That makes light summer clothing a sensible starting point, rather than packing mainly for autumn. Humidity averages 72%, so the warmth may feel sticky, particularly when you are active. Plan more energetic outings away from midday and leave room for shade breaks. Evenings remain warm, with an average night low of 22.5°C, so heavy layers are unlikely to earn much space in your bag. A light layer is still sensible for cooler spells, and cooling in your accommodation is worth considering if you struggle to sleep in warm conditions.

Mostly dry, with plenty of time outdoors

Rain is usually a minor consideration rather than a reason to rule September out. There are about 2 rainy days, so it makes sense to plan around outdoor time while keeping some flexibility for a wet spell. That monthly average does not promise an entirely dry stay or tell you when rain will arrive. Sunshine averages about 11.1 hours within 12.2 hours of daylight, giving you plenty of scope to shift activities away from the strongest midday sun. Pack sun protection and something light for rain rather than bulky wet-weather clothing. The balance suits travellers who want outdoor plans without making every day depend on perfect conditions.

The sea is a strong reason to go

At an average of 24.5°C, the sea is warm enough to make swimming a regular part of your holiday rather than a quick test of resolve. The September range across years is 23°C to 26°C, which supports choosing this month if sea temperature matters to you. Personal comfort still varies, but these are swimming temperatures rather than bracing ones. Pack with regular dips in mind, alongside light clothes for the warm air afterwards. This is a particularly good fit if you value time in the water more than very hot afternoons. Sea temperature alone, however, does not tell you how calm the water will be.