Meteorologists said temperatures were at the highest level in five years and would likely climb further by Saturday, reaching close to 90-year-highs of 40 degrees Celsius in the capital Bucharest. "The heat contributed to the death of 19 people," the health ministry said in a statement.
Television footage showed people jumping into the Dambovita river that crosses Bucharest or into fountains in front of Parliament's Palace, in an effort to cool down.
Authorities have put up 66 tents throughout the main cities in Romania to offer cold water and medical assistance to passers-by.
Drought is expected to last for the rest of the summer, affecting cereal crops and hydropower production, but temperatures should fall below 30 degrees Celsius from Wednesday, meteorologists said.