Hot? ...or REALLY Hot?

How can you tell when it's really hot outside? When you turn on the cold water tap, and can barely keep your hand in the water that comes out because it's too hot. Apparently it was 109F in Sydney today, fairly dry, but then there were clouds and a thunder shower. The heat then rain left a nice herbal scent in the air, but also seemed to bring out the flies. I am rethinking my notion of insulating the hot water pipes - maybe I need to insulate the cold pipes as well?!