Usually the weather was fairly predictable so rarely cancelled flights unless a hurricane was approaching or a tropical disturbance. Once we cancelled for two weeks when heavy smoke in the valley restricted visibility. Many times I had to hold for an hour for visibility to get to minimums. Only a few times did we end up at an alternate. A few times we delayed flights because 5km was required to land and wasn't expected until afternoon. When we flew the B727 there we couldn't land on 20 because of go around performance so diverted a lot more than the B757 because of the 5 knot tailwind rule.