Depends where you are. Generally, it's continental, and then there's the flatlands in the north (of Belgrade) and the mountains in the south.
Being continental means you get hot summers and cold winters, but not as much snow as, say, Canada, even though it's about the same lattitude as Toronto or upstate NY. In winter, the temperatures generally stay around zero, or single digits below, but then in february once in every 2-3 winters they go below -15, sometimes all the way down to -26, for maybe a week. Then come march, it's a lottery. The month being called mart, we say it's the domain of baba Marta (granny Martha), who is a rather capricious lady). First week of march can be anything - from -18 to +20. The trees may begin to blossom around 15th or in april (all this is about the north flatlands, I don't know enough of the south).
But then the springtime hits really fast and is rather nice, with different plants and trees blossoming at different times, all the way into june. Specially in the suburbs, where people have lots of fruit trees in their yards.
Summer used to be nice, with occasional afternoon showers, which would last fifteen minutes and then everything evaporates in an hour, but the last such year on (my) record was 2005. Lately, with all the chemtrails and other geoengineering, we get long draughts, which may start anywhere between mid-june to end of july, and drag into september. Record temperatures used to go up to 36, nowadays 42 is no miracle.
Early autumn is nice, and the miholjsko leto (aka Michael's summer aka indian summer) occurs two or three times, sometimes deep into october. November, then, is nasty and depressing - Tom Waits probably got inspired here. It's muddy, drenched, gray and murky. The arrival of frost is a relief - no more mud .