Just personal preference. The rand settings control the amount of change or "swing" in weather conditions when the game triggers a change in weather. In theory, a setting of "0" means little or no change, "1" some change, and "2" major change. In reality, these settings don't seem to make that much of a difference. Just to be on the safe side, though, I like to set mine to "1" because I prefer some change rather than none or very little (I like variety).
(NB: There is a possibility that the rand settings may also influence the priority of which weather state will change before the others. IOW, when all of the rand values are set to the same number, wind speed and direction seem to change most often. It might be interesting to see, for example, if setting WindRand = 0 and CloudRand = 2 changes this order in any way. Just a thought on my end--hasn't been tested).
IMO, the most important setting is WeatherRndInterval. This seems to control how soon the game will "roll" for a change in weather conditions. In my experience, setting this to "2" seems to result in slightly faster changes in weather--on average, 3-6 hours faster between weather changes than when this value is set to "5". As always, however, your mileage may vary.
Try both and see which one you like more. Although you can change these settings in the middle of a patrol without harm, I can't really remember if they take effect right away, after your next save, or only after the start of the next patrol. Try it and find out!
