Storms at sea are way too strong in this game. Time and again I have seen my fleets annihilated in a single turn. I never leave port in the winter, but even in the "safe" months, there is a high chance of finding your fleet gone before you can react. In the latest example I tried to cross the Adriatic Sea at its narrowest point, moving from one friendly port to another in May. The weather was fair at the beginning of the turn. There are only about 100 km of water separating the "heel" of Italy from land on the other side and there are only two sea regions to cross. Yet by the time I reached the other side, my 3 legions and 2 supply units were virtually gone. Only a couple hundred men remained. The fleet lost well over half it's strength as well. This type of result seems fairly common.
This really ruins the naval game imo. There is no way for the player to mitigate the danger of storms, and the effects are so dramatic that they easily throw the game. It would be impossible to conduct trade if the sea were really so hazardous. I can't imagine Rome and Carthage ever fighting each other if there was a good chance everyone would die every time they got on board a ship. I think the risk of storms is a good addition to the game in theory, but they need to be much milder.