Early Morning Fire Station Alarms

I have always been curious as to the type of 911 calls that always seem to happen around 4:00am. I live fairly close to a firehouse and always seem to hear sirens right before I awake in the morning. I can understand the accidental structure fire caused by transients in wintertime but what are the most common 911 calls that the fire department responds to in the wee hours of the morning? Thanks.

I've spent the last 20 years within a couple blocks of fire stations and have learned that most calls are medical. I think paramedics roll with one larger engine for support.