Some frosting of storm windows can be considered normal. I only ever encounter significant frosting when the temps go below 20*. You may have too much humidity in your house. It is difficult to get too much humidity inside in the winter, so maybe you have a problem, maybe not. Do you have any unvented gas heating appliances or a gas furnace or water heater with a blocked chimney causing exhaust gasses (with the water vapor) into your house? Most likely, you just have a normal side effect of single storms.