A heat wave is sweeping across Europe unusually early in the year, pushing temperatures above 30 degrees Celsius (86 Fahrenheit) in the UK and close to 40 degrees Celsius in Spain.

Britain has broken a May heat record lasting decades, while France issued its first-ever May heat alert.

Experts say a "heat dome" is trapping hot air over the continent.

Forecasters warn the summer will likely be warmer than average, as people and even zoo animals seek relief from the heat.