The maximum temperature that TotalBoat brand varnishes are designed for is based around normal environmental conditions. Conceivably, on a sunny day in the summer, a varnished piece of wood could possibly get as hot as 130-150°F, depending on geographic location. The varnish is designed to tolerate this, but it should not be pushed further. The hotter the varnish becomes, the resin will eventually start to soften from the heat. The natural expansion of the wood underneath can also cause some areas of the varnish to delaminate.