The climate of Corfu Island is Mediterranean, with mild, rainy winters and hot, sunny summers. The daily average temperature ranges from 9.5 °C in January to 25 °C in August.
Winter, from December to mid-March, is quite mild, even though it is not as mild as on the southern islands of Greece; moreover, it is rainy, especially in December and January, when up to 120 mm (4.7 in) of rainfall per month
Spring, from mid-March to May, is mild; the rains are quite frequent at the beginning, but then, they gradually become rarer, and fine weather becomes more and more frequent. May is a good month, before the summer heat.
Summer, from June to August, is hot and sunny: the maximum temperature exceeds 30 °C with some frequency, and can reach 35/36 °C, especially in July and August; at the worst, it can reach 40 °C. 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 Meltemi blows; as a consequence, here, the sea is warmer (see below).
Autumn, from September to November, is mild (initially even quite hot) and rainy. In September, there may still be many sunny days.
The best time to go to Corfu for a beach holiday runs from June to August, although the weather is often good also in the first half of September.
But if you plan to go hiking, walking or cycling across the island, you can go from mid-April to mid-June, in order to avoid the heat that can occur in high summer.