Temperatures soared across the Balkans, with parts of the region expected to hit 41 degrees Celsius (106 Fahrenheit), triggering heatwave health warnings.
In Croatia, the capital Zagreb and the country's east were at the highest risk of heat, according to the national Meteorological and Hydrological Service on Thursday.
Authorities remained on high alert after forest fires over the weekend destroyed dozens of homes on the country's tourism-oriented southern coast.
Albania said its firefighters managed to control eight blazes in the past 24 hours.
Meteorologists in Bosnia and Herzegovina warned people to stay indoors as parts of the country were predicted to climb to 41C.
"Be ready to suspend outdoor activities and prepared for high temperatures that will lead to health risks among vulnerable people, like the elderly and very young," Bosnia's meteorological institute said.
This is the first of at least three heatwaves expected during the June-August period in Bosnia, said Bakir Krajinovic from the country's Federal Hydro-Meteorological Institute.
Temperatures so far this month have already exceeded forecasts, and predictions for July and August indicate temperatures will be four to five degrees above average, Krajinovic said.
It was also the driest June on record in Bosnia, with the lowest rainfall since measurements began 135 years ago.
Krajinovic said climate change was driving "more intense" weather events and breaking records "more often".
Parts of Serbia are predicted to climb to 39C, also significantly above the seasonal average, according to Serbia's National Hydrometeorological Service.
The heat is expected to ease by Friday, with temperatures slightly dropping over the weekend, before climbing again next week, according to weather forecasts for several Balkan nations.
