TALLINN (Reuters) - A lot of Europe has felt like a sauna this month, which makes Willem Maesalu’s weird car seem even weirder: the bright yellow Audi 100 Avant is a rolling sauna.

Maesalu, 29, got the idea to convert his car a couple of years ago, when he found out it would be too expensive to rent a sauna for his birthday party. He and some friends spent two weeks remodeling the vehicle into a working sauna: a SaunAudi, as he calls it.

It has all the accoutrements of a traditional Finnish steam bath: wooden panels, thermometers and a wood-fired stove beside the steering wheel. Actually, a traditional Finnish steam bath hasn’t got a stove beside the steering wheel, because it is inert. But space was limited, and the stove had to go somewhere.

To use the sauna, Maesalu, 29, puts a chimney in the bonnet, fires up the wood stove, and heats the sauna to 60 degrees Celsius (140 degrees Fahrenheit). If it got any hotter, the windows might crack.

“The hardest part was figuring out where to put the heater and to find a way for the windows to not get too hot and break,” said Maesalu, a sprinkler systems maintenance technician and safety inspector.

The car can be driven, but Maesalu avoids taking it out on the road, since it lacks seats or seatbelts. Instead, he tows it around. He doesn’t take it out too often because insurance is expensive, for some reason.

Comfortably sitting four people, the SaunAudi has proved popular in Estonia, where others have previously converted vans or trucks. Maeslau has taken it to sauna festivals across Estonia and rents it out to steam lovers for 75 euros ($85) a day.