Opatija is situated in the north-eastern part of Istra between the 45°10' and the 45°28' of northern latitude and the 14°8' and the 14°20' of eastern longitude.

Thanks to its location below Učka, the climate is gentle with enough moister, and that is why Opatija is famous of rich vegetation and its parks. The bathing season lasts from June to the end of September, and winters are gentle. That makes the rest in Opatija pleasant through the whole year.

The salinity level of the Adriatic sea is, in general, equal to the Mediterranean 38.3%.
The sea temperature in summer is lower and in winter is higher than air temperature: in summer the surface temperature on the open sea is 22 - 25, and near the coast it is even higher than 25. The temperaturefalls with the depth. During winter in all Adriatic the average temperature is between 8 and 13.

Small daily temperature oscillations and high number of sunny days (up to 2500 sun hours per year) have positive effect on human organism.

In the coastal area, the most of the rain falls in October and November, while the driest months are July and August. Snow is rare phenomenon, and even if it falls, it holds just for a day or two,

The sea currents have no significant influence on navigation on the Adriatic sea.The tide oscillations are also small.
The most usual winds are bura, jugo and maestral.

Bura is specific coastal north-eastern wind; it is more frequent in winter than in summer and blows in gusts, sometimes even faster than 120 kilometer per hour. It raises waves to 2.5 meters high and brings mostly clear weather.

Jugo is warm and humid south-eastern wind that blows at constant speed, raising relatively high waves.

The people are especially fond of mestral, daily landward breeze that blows from the sea to the coast in the warmer part of the year and makes summer heats easier to endure.