Caravan to Hermosillo

[Dalillama]

Since this question(s) is directly related to the adventure adaptation, I'm putting it here instead of a new thread:
Are there published rules for seriously inclement weather/natural disasters anywhere, or is that more of a matter of winging it based on the specific situation? Dangerous sandstorms don't appear to be a feature of the area, despite the desert setting, but dangerous flash floods are completely appropriate, from both realism and narrative perspectives. I'm thinking a Survival (Desert) roll to know the flood is coming, with the amount of warning depending on the margin of success, but I'm not sure how fast the water will be moving, which will affect how long they have to get away, or what rules would be appropriate for dealing with being hit by the water.