Thanks to the high mountains surrounding Slovenia on all sides, its weather is greatly influenced by seasonal and local factors. Over the summer, a mild wind from the NW blows along the coastline with a force of up to 4 on the Beaufort scale (BFT). Daytime thermals work well here—that is, a regular and strong northwesterly wind (a daytime breeze or the Mistral), starts blowing at around 10:00 in the morning and continues through the day before abating at sunset. A katabatic wind (a cold, nocturnal wind that descends from the mountains into the valley) is typical for harbours in the northeastern part of the Adriatic Sea. During stable weather, this happens every day between 21:00 in the evening and 02:00 in the morning, and from 05:00 in the morning to 07:00 in the morning.
In the summer, a Sirocco (southeasterly wind) or a Bora may also occur. However, they do not normally last for more than 2-3 days. The Sirocco, unlike the Bora, will almost never exceed 7 BFT. The Sirocco is mostly cyclonic in nature and easy to predict (signs of an approaching Sirocco include a calm sea, light and variable wind, darkness on the horizon towards the south, increased temperature and humidity, and a gradual drop in pressure). The Tramontane (N) and Libeccio (SW, W) winds are extremely dangerous and unpredictable. They often occur when temperatures are high in summer and temperatures above the mountains at around 1 km above sea level are around zero. They bring with them very bad weather, zero visibility, and a wind of about 45 KN. In summer there are also thunderstorms, but they are usually over very quickly.
Average temperatures during summer are 22°C–25°C, though temperatures sometimes rise as high as 31°C. Despite that, Slovenia is in the northern part of the Adriatic, the sea is lovely and warm in the summer. The bay is not very deep, so the water in the sea is able to warm up.
In spring and especially in autumn, the wind is very unstable and often accompanied by strong thunderstorms. The dangerous Bora mainly blows here in winter. It is associated with stormy weather and can blow for up to 14 days. It blows from the NE (the direction is influenced greatly by the shape of the coastline) and can reach speeds of up to 100 KN. The Bora blows strongest in the Gulf of Trieste. Just as the Bora is frequent in the summer, the Sirocco (a strong south to southeasterly wind) is frequent in winter, blowing from North Africa. From October to May, this wind blows frequently, longer and with a greater force, up to 9 BFT. Because the Sirocco blows a long distance over the sea, it can create large 3–4 m waves. Dangerous locations are thus created off the Northern Italian coastline.