Can it withstand the impact of wind, hail and snow storms?  
  Yes! A solar water heater is well anchored to its foundation. The normal wind shearing force on the heater will neither damage the heater itself nor its foundation (Disastrous tornado-like storms excepted).

GSE evacuated tubes are designed to withstand hail size up to 25mm diameter.

Snow does not damage the heater physically. It only blocks the heat collection surface. The snow deposit on the heater collection surface is melted faster than that on the roof, because the tube glass surface is more slippery and slopping, causing the snow to slide down while melting.

Figure 1. A solar water heater installed on a slope roof.