Your May weather guide
WarmWeather in Kefalonia in May
May is a good time for Kefalonia if you want warm days rather than strong heat, but it is less convincing for a swimming holiday. Daytime highs average around 21°C, nights around 17°C and the sea around 19°C. For a UK traveller, that means weather suited to spending time outdoors, with a layer for evenings and some flexibility for rain. Go for comfortable warmth, not reliably hot beach days.
Long-term climate averages for Argostoli, not a forecast · 1991-2020
Kefalonia, month by month
Your snapshot
At a glance
The useful details for Argostoli.
- Average daytime high
- 20.9°C
- 9 in 10 days stay below 23°C
- Average night-time low
- 17.4°C
- coldest 10% of nights: 15°C or lower
- Compared with London
- +4.3°C
- London averages 16.6°C in May
- Sea temperature
- 18.9°C
- year to year: 18°C to 20°C
- Sunshine per day (est.)
- 9.4h
- 67% of 14.1 h of daylight
- Rainy days (1 mm+)
- 4
- 19 mm over the month
- Humidity
- 79%
- Days over 25°C
- 3%
- 0% over 30°C
- Record high 1991-2020
- 31.3°C
- 2020-05-17
- Record low 1991-2020
- 11.2°C
- 2019-05-09
- Flight from London
- ≈ 3 h 30 min
- 2166 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 6th warmest month of the year in Kefalonia and ranks 104th of 134 destinations we compare for May - see where else is hot in May. Within Greece it is 28th of 44 (Greece in May). Against London's average high of 16.6°C in May, Kefalonia is 4.3°C warmer by day and 9.1°C warmer at night.
Daytime and night-time in May
The typical May day in Kefalonia peaks at 20.9°C, but that is an average: the warmest 10% of days reach 23.4°C or more. Roughly 1 in 33 days top 25°C and 1 in 1000 pass 30°C. Nights average 17.4°C; one night in ten drops to 14.9°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest May day here reached 31.3°C (2020-05-17) and the coldest night 11.2°C (2019-05-09).
Rain in May
Some rain (4-8 rainy days): about 4 days with 1 mm or more, 19 mm in total. Year to year it varies a lot - the wettest May was 1991 with 67 mm, the driest 2004 with 1 mm. Humidity averages 79%.
Sea temperature in May
The sea averages 18.9°C - bracing (18-22°c). Depending on the year it ranges from 17.9°C to 19.8°C. For the warmest sea here, come in August (26.0°C).
Sunshine and daylight
Around 9.4 hours of sunshine a day (estimated from cloud cover), 14.1 hours of daylight: the sun rises about 06:27 and sets about 20:42 local time in mid-May. Average cloud cover is 33%.
Is May a good time to visit Kefalonia?
It is a reasonable choice: warm days. The best months for Kefalonia on our scoring are July, August, June; months averaging 25°C or more: Jul, Aug, Sep.
Warm enough for light clothing, not dependable heat
The average daytime high of 20.9°C makes May a sensible choice if you prefer being outdoors without intense heat. Light clothing should suit warmer afternoons, but pack a jumper or light jacket rather than relying entirely on summer clothes. Nights average 17.4°C, with the coldest nights reaching 14.9°C or lower, so sitting outside after dark can feel cool. Days reaching 25°C account for just 3%, which is the main catch if your idea of a Greek holiday involves consistently hot afternoons. May suits travellers who prioritise comfortable daytime temperatures over heat that keeps going into the evening.
Plenty of sunshine, with room for rain
May brings about 9.4 hours of sunshine within 14.1 hours of daylight, giving you a generous window for outdoor plans without needing every hour to be sunny. Rain is still part of the picture, with about 4 rainy days during the month. That is a reason to bring a light waterproof and keep plans flexible, rather than a reason to rule May out. Do not assume your particular stay will follow the monthly pattern exactly. Use the brighter spells for time outside, carry sun protection, and leave yourself the option to change plans when the weather turns.
The sea is the bigger compromise
The sea averages 18.9°C in May, putting it firmly in the bracing category rather than the comfortably warm one. Its year-to-year range of 18°C to 20°C means even a warmer May is not a strong bet for leisurely swimming. If you enjoy a brisk dip, that may be an acceptable trade-off for the mild air temperatures. If you want to spend long stretches in the water, May is harder to recommend. Pack swimwear if you are happy with cool water, but make the trip about being outdoors rather than assuming the sea will be the main draw.
A little perspective
Kefalonia 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 | 13.5°C | 10.8°C | 16.0°C | 4.6 | 117 | 12 | 0% |
| February | 13.4°C | 10.6°C | 15.2°C | 5.3 | 101 | 11 | 0% |
| March | 14.9°C | 11.8°C | 15.1°C | 6.4 | 78 | 10 | 0% |
| April | 17.2°C | 13.9°C | 16.0°C | 7.8 | 41 | 7 | 1% |
| MaySelected | 20.9°C | 17.4°C | 18.9°C | 9.4 | 19 | 4 | 3% |
| Junebest | 24.8°C | 21.2°C | 22.5°C | 12.1 | 11 | 2 | 45% |
| Julybest | 27.1°C | 23.6°C | 24.6°C | 13.6 | 5 | 1 | 91% |
| Augustbest | 28.0°C | 24.5°C | 26.0°C | 12.4 | 7 | 1 | 99% |
| September | 25.2°C | 22.2°C | 25.0°C | 8.9 | 63 | 6 | 56% |
| October | 22.0°C | 19.1°C | 22.8°C | 6.5 | 104 | 9 | 5% |
| November | 18.4°C | 15.7°C | 20.3°C | 4.8 | 154 | 12 | 0% |
| December | 14.9°C | 12.3°C | 17.7°C | 4.3 | 156 | 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.
Malta · 21°C by day · sea 19°C
Valletta
Italy · 22°C by day · sea 18°C
Puglia
Italy · 20°C by day · sea 19°C
Sorrento
Spain · 22°C by day · sea 20°C
Tenerife
Italy · 20°C by day · sea 19°C
Amalfi Coast
A little more detail
Kefalonia in May FAQs
Plain answers, grounded in the averages.
Is Kefalonia hot in May?
Kefalonia is warm in May: the average daytime high is 20.9°C and nights average 17.4°C. Roughly 1 in 33 May days reach 25°C.
Can you swim in the sea in Kefalonia in May?
The sea around Kefalonia averages 18.9°C in May, which is bracing - fine for a quick dip, cool for long swims. Between 1991 and 2020 it ranged from 18°C to 20°C depending on the year.
How much does it rain in Kefalonia in May?
Kefalonia sees about 4 rainy days (1 mm or more) and 19 mm of rain in a typical May. The wettest May between 1991 and 2020 was 1991 (67 mm) and the driest was 2004 (1 mm).
How sunny is Kefalonia in May?
Kefalonia gets around 9.4 hours of sunshine a day in May out of 14.1 hours of daylight (estimated from average cloud cover).
How does Kefalonia compare with the UK in May?
Kefalonia is on average 4.3°C warmer than London by day in May (20.9°C against 16.6°C).
What is the hottest May on record in Kefalonia?
Between 1991 and 2020 the hottest May day in Kefalonia reached 31.3°C on 2020-05-17, and the coldest night dropped to 11.2°C on 2019-05-09.
How much warmer is Kefalonia than London in May?
Kefalonia's average daytime high is 20.9°C, compared with London's 16.6°C, a difference of 4.3°C. That is a useful step up in warmth, but it points to milder outdoor days rather than a guarantee of hot weather.
Should I choose May or a summer month?
Choose May if comfortable warmth matters more than strong heat and you can accept bracing sea temperatures. July, August and June are the better-rated months overall, so consider those instead if May's modest warmth sounds like too much of a compromise.
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 Argostólion (Argostoli). Sea temperature from the nearest 5 km sea cell, 1.4 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