The climate of Zakynthos (or Zante), a Greek island of the Ionian Sea, is Mediterranean, with mild, rainy winters and hot, sunny summers.
Here are the average temperatures.
Zakynthos - Average temperatures
Min (°C)889111418202119161210
Max (°C)141416192328313128231916
Min (°F)464648525764687066615450
Max (°F)575761667382888882736661

Rainfall is quite abundant, in fact, it amounts to nearly 1,000 millimeters (40 inches) per year, but it is concentrated in the period from October to March, while in May and September, it rains little, and from June to August it almost never rains. Here is the average precipitation.
Zakynthos - Average precipitation

Winter, from December to mid-March, is mild but rainy, especially in December and January, when more than 150 millimeters (6 inches) of rain fall per month. However, there is a moderate amount of sunny days too. The island is sheltered from cold spells, so much so that it never snows at sea level, while in inland hills, which reach 758 meters (2,487 ft) above sea level, sometimes it can snow, as happened in February 2012. Sometimes, however, a cold wind from the north can blow, and in the winter months, the minimum temperature at sea level can drop to 0 °C (32 °F).

Spring, from mid-March to May, is mild; the rains gradually become rarer, and sunny days become increasingly more frequent. May is a pleasant month, before the summer heat.

Summer, from June to mid-September, is sunny and hot: the maximum temperature often exceeds 30 °C (86 °F) and can easily reach as high as 35 °C (95 °F), especially in August; in the worst moments, it can reach 40 °C (104 °F), as happened in August 2006. Luckily, sea breezes blow, providing relief, at least when the heat is not excessive, and in any case, you can cool yourself in the sea. This part of Greece, overlooking the Ionian Sea, is outside the area where the annoying but cooling wind called Meltemi blows, so the sea is warmer as well.

Autumn, from mid-September to November, is mild (and initially warm enough) and rainy. In October, there may still be many sunny days.

Zakynthos, sea and coast

The amount of sunshine in Zakynthos is great in summer, when clear skies prevail, but it is also good in spring, when days with clear skies are already frequent. In contrast, From November to February, sunny days alternate with periods of bad weather. Here are the average sunshine hours per day.
Zakynthos - Sunshine

The temperature of the sea, which, as mentioned, is higher than in the Aegean Sea, is warm enough for swimming from July to September, while in June and October, it's around 22 °C (72 °F), so it's a bit cool. Here are the average sea temperatures.
Zakynthos - Sea temperature
Temp (°C)161515161822242625222017
Temp (°F)615959616472757977726863

Best Time

The best time to go to Zakynthos for a beach holiday runs from June to mid-September.
The turtles Caretta caretta arrive on the beaches to lay their eggs in June.
The month of May is preferable for excursions on the island, or maybe also the first half of October, since in summer, it can be too hot for this kind of activity.

Back to the Ionian Islands.