Step 1 : Introduction to the question "3. What event is the most common "trigger event" in urban riots?"
...1. false rumors 2. extremely hot humid weather 3. a normal police event such as an arrest 4. all of these All these "trigger events" seem to occur in most urban riots, either singly or in some combination, especially the hot humid weather. Not many, if any at all, have occurred in the winter.
