"Extreme wildlife alert throughout Spain, maximum precaution," the ministry of agriculture said in a Twitter message.
Spain's national weather office put nearly all of the country on "red" alert for wildfires, the highest level in the five-stage scale, warning of an "extreme" risk of blazes.
Temperatures are expected to reach 40C (104 Fahrenheit) in the centre and southeast of Spain on Monday.
In the rest of Spain temperatures will soar to between 36C and 38C.
The heatwave which arrived from northern Africa is forecast to last at least until Sunday.
It is Spain's second heatwave of the summer. Last week the weather office warned people to take extra precautions, especially the elderly, as temperatures soared as high as 44 Celsius in the southern city of Cordoba on June 29th.
A wildfire that broke out on Saturday in Aragon that forced the evacuation of some 1,500 people from their homes was brought under control on Monday, the regional government said in a statement.
The blaze ravaged around 13,500 hectares (33,500 acres) of pine forest and brush.
Firefighters remained on alert at the scene due to high temperatures and strong winds, the regional government said.
About 500 rescue workers and firefighters were deployed to fight the blaze.