Experience in recent disaster assistance programmes in Kosovo and Afghanistan illustrates how ill equipped the aid community is to deal with cold weather affecting transitional settlements.
To form a tornado, cold air must sit above warm and moist air, and the wind needs to go in different directions at different heights, creating shear forces.
So I've been recharging it outside in the cold, including days when the windchill factor was about minus 5, and it worked fine, illuminating a dim corner of my kitchen.
On a chilly day last spring, a few dozen developers of children's apps for phones and tablets gathered at an old beach resort in Monterey, California, to show off their games.