Weather in Croatia-Slovenia late April-Early May

Jonathan - The weather will be in the mid 50's in Croatia and Slovenia and there will be some rain on occasion.

There are several weather sites you can check to find historical weather data. Friends of ours visited Croatia and Slovenia last spring in late April and early May, so similar to your dates. They told us the weather was a mixed bag. They did have a lot of rain and cooler temperatures. They told us it was raining and 47F in Ljubljana. I realize weather can change from year to year, but I would plan for some rain (maybe lots of rain) and cooler temps. Make sure you have appropriate clothing, and plan to dress in layers.

Are you going to Plitvice Lakes National Park? Based on our friends experience, I think Plitvice might be more impressive during the spring because of more rain. We were there this past September, and while it is a beautiful and impressive park, I don't think there was as much water in September as there was in the spring. So seeing Plitvice in the spring might be a bit more impressive than in September.

Croatia is a long, skinny country. Low-temperature averages for April are a lot lower in Zagreb (inland and to the north) than in coastal Dubrovnik to the south. Ljubljana's averages are similar to Zagreb's, and I'd guess Lake Bled is similar to Ljubljana. The average lows for those northern destinations are 41.4 to 42.4 F in April. Your travel period is one of the wettest of the year, with the number of rainy April days ranging from 12.5 to 14.

However, averages hide extremes, those particular averages are based on periods ending in either 2000 or 2010, and weather seems to be increasingly variable; therefore, I'd highly recommend checking the actual, day-by-day weather statistics on the website timeanddate.com for your travel dates over at least the last 3 to 5 years.

Cool with rain creating the opportunity to walk on narrow cobblestone "streets" amidst few other tourists. Hot soups with thick bread sates a cold belly. Holding a loved ones hand while taking a romantic stroll warms the heart.

we were sailing the Dalmatian coast mid May 2019 and it was rainy and in the 70's. We had this trip planned for two years and it seems to me the prior years it was more like mid 80's. Last spring was pretty crummy all over Europe. I don't think you can predict the weather you just have to plan accordingly when you pack - layers is the key

You certainly can't predict the weather. I think it's helpful to look at actual daily temperatures to see how wide the range is. A mix of 45 and 75 is an average of 60. I'd rather know it is sometimes as cold as 45 and sometimes as hot as 75. But I am a very weather-focused traveler.