On the coast, the temperatures can be in the 70's (F). Not exactly hot, but warm. Also, the month of September can have a wet climate, cooling it off slightly.
hot (VRUCE)
Yes in summer
Vladimir Pogacic was born on September 23, 1919, in Karlovac, Croatia, Yugoslavia [now Croatia].
Ferdo Pomikalo died on September 16, 1973, in Zagreb, Croatia, Yugoslavia [now Croatia].
Robert Naprta was born on September 19, 1967, in Zadar, Croatia, Yugoslavia [now Croatia].
Mladen Vulic was born on September 1, 1969, in Vinkovci, Croatia, Yugoslavia [now Croatia].
Blazenka Jencik died on September 28, 1984, in Zagreb, Croatia, Yugoslavia [now Croatia].
Lidija Jojic was born on September 1, 1912, in Imotski, Croatia, Yugoslavia [now Croatia].
Miranda Leonhardt was born on September 11, 1975, in Split, Croatia, Yugoslavia [now Croatia].
Incomparable Croatia - 2013 was released on: USA: 6 September 2013 (TV premiere)
Dinko Simunovic was born on September 1, 1873, in Knin, Croatia, Austria-Hungary [now Croatia].
Dado Topic was born on September 4, 1949, in Nova Gradiska, Croatia, Yugoslavia [now Croatia].