Your May weather guide
WarmWeather in Istanbul in May
May is a good time for Istanbul if you want comfortable city weather rather than summer heat. Average daytime highs of 20°C suit walking around, while nights near 14°C call for a light jacket. The catch is the sea: at 15.4°C, it is cold for swimming. For a UK traveller, this is a trip for spending time outdoors with layers and a rain backup, not for guaranteed hot sunshine.
Long-term climate averages for Istanbul, not a forecast · 1991-2020
Istanbul, month by month
Your snapshot
At a glance
The useful details for Istanbul.
- Average daytime high
- 20.0°C
- 9 in 10 days stay below 24°C
- Average night-time low
- 13.6°C
- coldest 10% of nights: 10°C or lower
- Compared with London
- +3.4°C
- London averages 16.6°C in May
- Sea temperature
- 15.4°C
- year to year: 14°C to 16°C
- Sunshine per day (est.)
- 7.8h
- 55% of 14.3 h of daylight
- Rainy days (1 mm+)
- 6
- 36 mm over the month
- Humidity
- 76%
- Days over 25°C
- 6%
- 0% over 30°C
- Record high 1991-2020
- 30.6°C
- 2013-05-23
- Record low 1991-2020
- 5.0°C
- 2011-05-07
- Flight from London
- ≈ 3 h 54 min
- 2491 km, short-haul (estimate for a direct flight)
Records are observed extremes within 1991-2020, not typical holiday conditions. Warm-day percentages are shares of days, not day counts.
How May compares
May is the 5th warmest month of the year in Istanbul and ranks 117th of 134 destinations we compare for May - see where else is hot in May. Within Turkey it is 16th of 18 (Turkey in May). Against London's average high of 16.6°C in May, Istanbul is 3.4°C warmer by day and 5.3°C warmer at night.
Daytime and night-time in May
The typical May day in Istanbul peaks at 20.0°C, but that is an average: the warmest 10% of days reach 23.8°C or more. Roughly 1 in 18 days top 25°C and 1 in 1000 pass 30°C. Nights average 13.6°C; one night in ten drops to 10.3°C or lower, so pack a layer for evenings - it is genuinely cool after dark. Between 1991 and 2020 the hottest May day here reached 30.6°C (2013-05-23) and the coldest night 5.0°C (2011-05-07).
Rain in May
Some rain (4-8 rainy days): about 6 days with 1 mm or more, 36 mm in total. Year to year it varies a lot - the wettest May was 1998 with 105 mm, the driest 2003 with 2 mm. Humidity averages 76%.
Sea temperature in May
The sea averages 15.4°C - too cold for most (under 18°c). Depending on the year it ranges from 14.2°C to 16.3°C. For the warmest sea here, come in August (24.4°C).
Sunshine and daylight
Around 7.8 hours of sunshine a day (estimated from cloud cover), 14.3 hours of daylight: the sun rises about 05:46 and sets about 20:15 local time in mid-May. Average cloud cover is 45%.
Is May a good time to visit Istanbul?
It is a reasonable choice: warm days. The best months for Istanbul on our scoring are August, July, June; months averaging 25°C or more: Jul, Aug.
Comfortable afternoons, cooler evenings
Plan around mild afternoons rather than packing as though it is midsummer. A daytime high of 20°C makes walking a reasonable prospect without having to organise everything around avoiding midday heat. Warmer spells do happen, but only 6% of days reach 25°C, so shorts and summer tops should not be your whole wardrobe. Bring light layers, long trousers and a jacket you are happy to carry during the day. The coldest nights can fall to 10.3°C or below, making that extra layer useful if you stay out late. May suits travellers who prefer warmth without relying on consistently hot days.
Plenty of daylight, but keep plans flexible
There is useful time for being outdoors, with about 7.8 hours of sunshine within 14.3 hours of daylight. That leaves room to take your time rather than squeeze everything into a short bright spell, though daylight does not mean uninterrupted sun. About 6 rainy days make a light waterproof sensible, with indoor plans available when showers interrupt the day. Rain is a consideration rather than a reason to rule May out, but do not assume your visit will stay dry. Swimming is the clearer compromise: the sea averages 15.4°C and remains cold across its usual range. Choose May for time around the city, not for comfortable dips in the sea.
A little perspective
Istanbul through the year
May is highlighted. See how it compares with the rest of the year.
| Month | Day | Night | Sea | Sun/day | Rain mm | Rainy days | Days 25°C+ |
|---|---|---|---|---|---|---|---|
| January | 8.2°C | 4.1°C | 8.4°C | 3.1 | 85 | 12 | 0% |
| February | 8.8°C | 4.1°C | 7.3°C | 3.7 | 71 | 11 | 0% |
| March | 11.0°C | 5.6°C | 7.8°C | 4.8 | 72 | 11 | 0% |
| April | 15.1°C | 8.8°C | 10.2°C | 6.2 | 47 | 8 | 0% |
| MaySelected | 20.0°C | 13.6°C | 15.4°C | 7.8 | 36 | 6 | 6% |
| Junebest | 24.9°C | 18.4°C | 20.8°C | 10.4 | 35 | 6 | 50% |
| Julybest | 27.6°C | 21.1°C | 23.5°C | 11.8 | 19 | 4 | 88% |
| Augustbest | 27.9°C | 21.8°C | 24.4°C | 10.8 | 20 | 3 | 91% |
| September | 24.1°C | 18.5°C | 22.5°C | 8.2 | 45 | 6 | 42% |
| October | 19.2°C | 14.5°C | 18.9°C | 5.3 | 78 | 9 | 4% |
| November | 14.4°C | 10.0°C | 14.8°C | 3.9 | 72 | 10 | 0% |
| December | 10.2°C | 6.3°C | 11.1°C | 3.0 | 97 | 13 | 0% |
Day = average daytime high, night = average night-time low, 1991-2020.Sun is hours per day; rainy days count 1 mm or more.
Day, night and sea
Monthly average temperatures, 1991-2020
- Day
- Night
- Sea
Best months here
On warmth, low rainfall and sunshine, start with these.
Keep exploring
Similar in May
Closest matches on daytime temperature, sea temperature and sunshine, in other countries.
Bulgaria · 20°C by day · sea 16°C
Sunny Beach
Portugal · 20°C by day · sea 15°C
Porto
Portugal · 21°C by day · sea 17°C
Lisbon
Croatia · 20°C by day · sea 17°C
Pula
Spain · 21°C by day · sea 17°C
Barcelona
A little more detail
Istanbul in May FAQs
Plain answers, grounded in the averages.
Is Istanbul hot in May?
Istanbul is warm in May: the average daytime high is 20.0°C and nights average 13.6°C. Roughly 1 in 18 May days reach 25°C.
Can you swim in the sea in Istanbul in May?
The sea around Istanbul averages 15.4°C in May, which is cold for swimming without a wetsuit. Between 1991 and 2020 it ranged from 14°C to 16°C depending on the year.
How much does it rain in Istanbul in May?
Istanbul sees about 6 rainy days (1 mm or more) and 36 mm of rain in a typical May. The wettest May between 1991 and 2020 was 1998 (105 mm) and the driest was 2003 (2 mm).
How sunny is Istanbul in May?
Istanbul gets around 7.8 hours of sunshine a day in May out of 14.3 hours of daylight (estimated from average cloud cover).
How does Istanbul compare with the UK in May?
Istanbul is on average 3.4°C warmer than London by day in May (20.0°C against 16.6°C).
What is the hottest May on record in Istanbul?
Between 1991 and 2020 the hottest May day in Istanbul reached 30.6°C on 2013-05-23, and the coldest night dropped to 5.0°C on 2011-05-07.
Is Istanbul warmer than London in May?
Yes. Istanbul's average daytime high is 20°C, compared with 16.6°C in London, a difference of 3.4°C. That is a useful step up in warmth, but not a jump into reliably hot summer weather. You will still want layers for evenings.
How long is the flight from London?
The flight from London takes about 3 hours 54 minutes, putting Istanbul within short-haul reach. May's mild daytime weather makes it a sensible option for a city break if swimming and strong heat are not priorities.
Should I go in May or wait until summer?
Choose May if comfortable walking weather matters more than heat and swimming. August, July and June rate more highly overall for weather, so look towards those months if May's mild days and cold sea do not fit the holiday you want.
About these averages
ERA5-Land climate reanalysis via Open-Meteo (11 km grid) and NOAA Coral Reef Watch 5 km sea temperatures, 1991-2020
Averages computed from daily values at Istanbul. Sea temperature from the nearest 5 km sea cell, 2.5 km from that point. Sunshine hours are estimated from average cloud cover.Records are the highest and lowest daily values in that 30-year period, not all-time records. These are climate averages, not a forecast for your trip. How we measure holiday weather
- Hot · 25°C+
- Warm · 20°C to below 25°C
- Mild · 15°C to below 20°C
- Cool · below 15°C