Question for warmist Bill McKibben: If warm weather really causes tornadoes, why isn't the current US heatwave accompanied by lots of tornadoes?

Heatwave, Drought Threaten Crops, Livelihoods Across U.S. - International Business Times

The soaring temperatures scorching states from Illinois to Texas have done more than cause discomfort -- a record drought is battering farmers and ranchers whose crops are withering and whose livestock are going unfed.

A link between climate change and Joplin tornadoes? Never! - Warmist Bill McKibben - The Washington Post

[May 23, 2011] Caution: It is vitally important not to make connections. When you see pictures of rubble like this week’s shots from Joplin, Mo., you should not wonder: Is this somehow related to the tornado outbreak three weeks ago in Tuscaloosa, Ala., or the enormous outbreak a couple of weeks before that (which, together, comprised the most active April for tornadoes in U.S. history). No, that doesn’t mean a thing.