Climate in Croatia - Coast
Croatia has two climates, as you may well expect. The coast has a typically Mediterranean climate consisting of hot, dry, sunny weather during summer, and relatively mild - though somtimes wet - weather in winter.

Average temperatures during summer should lie in the mid-to-high 20s °C/77-86°F, though it's more likely that you'll have temperatures well into the 30s °C/high 80s or low 90s °F.

Winters are obviously cooler, though temperatures never really get below about 5°C/41°F. Anything colder than this is considered freak weather, though technically not impossible - February 2009 saw snow in parts of Dalmatia, such as Zadar and Split - see photos of the snow from that time! (Having said that, I suppose wherever you're from, you've been subjected to some freak weather in the last few years!) You will still experience some sunny days, though it can be reasonably rainy during winter.

Climate in Croatia - Interior
In the interior, there's a continental climate which means that winters can be pretty cold, with temperatures often falling below 0°C/32°F. Snow is very likely, and can be pretty heavy during the winter.

Summers, on the other hand, can very often be sweltering with temperatures often reaching the mid to high 30s °C/high 80s or low 90s °F and when there's no cool sea breeze (or the sea itself!), it can get a little uncomfortable at times. Officially, average temperatures in the interior would be around the low 20s °C/low 70s °F but, from personal experience, it will be much hotter.

Air-conditioning is becoming more and more common in Croatia all the time, so wherever you are during summer, so your accommodation (hotel or private) may well have it, providing you with a bit more comfort in summer. Air-con is also pretty common in cafes, restaurants and bars these days.

Weather - when should I go?
If you thinking of the weather in terms of the best time to go to Croatia, we'd advise September...or possibly May. September still has glorious weather and by that stage of the year, the sea will still be warm. May is also a great month to visit Croatia, as temperatures have already risen to a pleasant level and you'll have more and more sunny days, but will be without any of sweltering heat that will make you want to lie down every half an hour. Oh and, better still, you'll avoid the crowds in either of these months!

The Bura
One reasonably famous - or most likely, infamous - aspects of Croatian weather that you may have heard mentioned, or even experienced yourself, is the "bura". The bura is a very strong north-easterly wind that blows towards the coastline, generally in Dalmatia, and is felt strongest around the Velebit mountain range. It normally occurs in winter though some of its effects can be felt year round. The strong wind occurs due to the two different climate types clashing and, as such, the wind is considered unpredictable and strong gusts can happen rather suddenly. Wind speeds can reach over 125 miles/200 kilometres per hour, although you're unlikely to ever come across winds that strong. Unsurprisingly, the bura causes disruption to those sailing off the coast, though problems to traffic and so on can also occur on land

More information
You can find all sorts of weather and climate statistics at the Croatian Meteorological Service website.