Over a period of 4 weeks in the Ionian
in April you can expect between 2 and 4 periods of unsettled weather; the rest of the time will be sunny with light winds and very nice.
Periods of unsettled weather can last from 2 to 4 days. They are the periods when there is significant cloud cover, usually associated with a low. Small wind gradients at these latitudes can create brisk winds as the low approaches or recedes. These may last up to 12 hours or so, but as pointed out above, rarely reach force 7 or more. Periods of unsettled weather are well forecast
, and at least half of them bring heavy rain.
What is a lot more vicious is when these periods contain nests of thunderstorms. This is much less common in spring than in autumn. However, thunderstorms bring the risk of short periods (15 - 30 mins) of extreme wind - 40kts or so. Knock you over stuff.
So you may be lucky in a month - only 2 sessions of unsettled weather, one with significant rain, and no thunderstorms. Or you may be unlucky, with four sessions - 12 days of cloud, 6 with significant rain, and 2 sessions of thunderstorms. A bit like a bad British summer.
It all depends where the jet streams are running that year.
The above observations are based on 15 years of charter
operations in the Ionian
, usually preparing boats, chartering them only in late April. On average, too wet before that!