What's the best way to get your toddler to stop screeeeaming in public?

Today we went out to lunch and our 2 year old son screeeamed at the top of his lungs, the LONGEST , shriekiest scream you've ever heard. A hush fell over the entire restaurant and when we told him to stop he kept shrieking even more! Seriously, it was 100 degrees out today, so going to the car was not an option. Taking him to another part of the restaurant would only have resulted in more of a meltdown that never ends. My husband threatened to go do time out and he just screamed. What do you do??? It's ridiculous!