The highest day temperature in September 2026 was 86°F. The lowest night temperature was 55°F. The average values for day and night temperatures during September were 75.4°F и 66.4°F respectivly.

The average sea surface temperature in September 2026 for Opatija was 77.3°F. The maximum and minimum values were 72.2°F and 81.6°F respectively.

Most of the days in September are sunny but you can also expect cloudy and gloomy days.

Precipitation total in September for Opatija is 3.6 in. It makes september one of the most rainy months of the year.

The average wind speed in September is 6.6 mph. This value is relatively stable throughout the year.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for Opatija in September is 8.8 hours.