How sensitive are cats to heat?

The answer lies in the type of heat: ambient or directional. Cats like to lie in front of a fire. It feels too hot for us but our cat finds it acceptable. This is because the cat's coat protects the cat from the heat directed at her/him. Clive Dalton on Knol, a Google website subdomain, says that cats are not very sensitive to heat and then refers to the cat lying besides the fire at over 50ºC.  A fair point.

He is correct, but cats do not tolerate high ambient temperatures as well as people. Cats don't sweat that much. They sweat on their paws. Cats lose heat by panting and licking fur to use the latent heat of evaporation of their saliva to cool themselves.

Cats can overheat - heatstroke - which leads to rapid breathing, very red mucous membranes, and vomiting.  The cat's body temperature rises to over 106º F (41º C). If left untreated heat stroke can lead to coma and death.

Therefore, cats are more sensitive to high temperatures than us. That, I think, makes them sensitive to heat.