Telling Grandma/grandpa to use an ebike in the snow or in lethal wet bulb temperatures isn't a real solution. It's great that it worked for your folks but it cannot work for mine.
The air can be so saturated with water that you cannot evaporate sweat which is the primary way your body sheds heat.
It is unsafe for anyone, let alone the elderly, to travel in these conditions unless you have a vehicle with climate control.