May is a great time to relax in Croatia, if you do not like the grueling heat. The average temperature during the day during the month varies from 14 to 21 degrees. However, towards the end of the month, the air warms up to 25 degrees in the daytime. This is a very comfortable temperature for sunbathing.
It is also worth remembering that the average temperature of water in May is from 17 to 20 degrees. The swimming season is not yet open, as the water in the sea is pretty cool. However, by the end of the month in some areas, water can be heated to 21 degrees or more. At this time, the first bathers "go" to the Adriatic Sea.
If you talk about the weather in some cities in Croatia, then in Zagreb the average daytime temperature in May is 19, and at night - 7 degrees. In Dubrovnik, daytime temperatures reach an average of 22, and at night - 14 degrees. The water heats up to 19 degrees. In Zadar, the daytime temperature is 21 degrees, and the night temperature is 13 degrees. The water has a rather cold temperature for swimming - 17 degrees.
The weather in May is perfect for long trips around the country, for trips to museums and walks around the cities. So you can enjoy an excursion type of holiday in full. In addition, you will avoid the problems associated with a large influx of tourists (falls in July-August): the queues in museums, "overpopulation" of beaches, the lack of places in hotels, seasonal price increases, etc.