Due to geographical diversity, Croatian regions differ among each other in climate as well – from moderately warm and rainy climate in the interior, through cold winter climate in the mountain regions, to warm Mediterranean climate in the coastal area and on the islands.
In the coastal regions, average January temperatures range from 5°C to 9°C. In August they vary from 22°C to 25°C average, with sea temperatures from 12°C in winter to 25°C in the summer. Spring and autumn (April, May and October) are usually pleasantly warm, with somewhat stronger winds, which is attractive to more experienced yachtsmen.
Different types of wind that appear on Adriatic bring different problems or ease, for both locals and sailors. Bora is cold, abrupt and dangerous wind, but it also brings clear weather and fresher air. This is why most people like it better than sirocco (jugo, SE wind) which brings “heavy” air and low air pressure that cause headaches, bad mood and similar problems, especially in Dalmatia.
This cold SE wind blows from the mainland towards the open sea and brings bright weather. It starts suddenly and blows in gusts, strongest of which are in the Velebit channel and Gulf of Trieste. In the summer Bora is not as strong and abrupt as it is in winter. It lasts for a few day (sometimes less than 24 hours), but in winter it can last for up to two weeks.
Bora can be very unpleasant for smaller boats. Her vehement temper is the most dangerous thing about it, particularly for less experienced yachtsmen. As it appears suddenly and blows in gusts, it is very difficult to foresee it, and in the coastal area she reaches the speed of 40-50 knots (even more in winter).
If Bora catches you at sea, the best thing to do is try to find some shelter at the SW foothills of the islands (the higher the island, the better).
Warm SE wind, known as sirocco, is created in the cyclone area and brings clouds, rain and low air pressure from the Mediterranean and south parts of Adriatic. It develops gradually and it usually can be noticed two or three days in advance, so you can plan finding a safe shelter.
Sirocco is also responsible for very high waves, especially in the channels, and the best thing to do is to find cover in the nearest marina. However, if it catches you at sea, you should hide at the NE side of the islands.
In summer, sirocco appears as the local wind (particularly in the south Adriatic), but in winter it often reaches north Adriatic as well.