It depends on the terrain and whether or not the area has snow-removal equipment. Seattle rarely got snow and the hills are quite steep. The snow is usually wet and slippery. If the buses couldn’t go up the hills in 1/2 inch of snow, then school closed. If there are no shoulders to the roads and the bus happens to drop one wheel off the edge, the bus rolls over. Not a good combo.
School is extended at the end of the year if schools close because of snow, etc. There is also a state mandate for the number of days of school per year, usually 180. Therefore, the districts end up with the same amount of money.
I thought we grew moss and mold! :D