A nuclear blast is an explosion with intense light and heat, a damaging pressure wave, and widespread radioactive material that can contaminate the air, water, and ground surfaces for miles around.
On the other hand if they ask you to water their plants otherwise they'll set their TV on full blast while they're on holiday, it immediately gets your hackles up.
In a rare blast of temper over dinner one night, the elder Mr. Gates reacted to a bitter mother-son argument by pitching a glass of cold water in young Bill's face.