People are in a good mood, a bit lazy and might not pay attention watching their valuables and locking their vehicles. Some some people this environment is a great place for car burglary. Criminals just don't care you are having a good time.
It's also a great place to have a few drinks and since you are so relaxed and due to the sun you might for the moment forget you still have to drive. Unfortunately this also results in to much driving under influence of alcohol.
Normal warning signs just don't work anymore. Nobody pays attention. What other ways are there to get the peoples attention. When I arrived in town the temporary welcome sign immediately caught my eye and I kept watching. It displayed a set of rotating messages, starting with a welcome and continuing with a few warning. I felt that the police was engaging with me and really wanted to help.