When I say high rainfall, that is of course relative.  Ours is 22", which is comparable to most of eastern ND.  But since we have such low pan evaporation rates and temperatures, that is far in excess of what we usually need, and excess rain is often our limiting factor on most acres.  

Compared to the rest of western Canada, we are the wettest farmland( with the exception of a few places in Manitoba) and the coldest place that tries to farm.  Combine that with heavy deep clay soils with nearly impermeable subsoil, and dust is a rare event.  Not much moisture in the winter, but we often have snow on the ground for 5 months.  Did see a neighbors tilled field blowing dirt the winter before this due to almost no snow cover, so it can happen.