Hail can have devastating consequences. Where just was warm summer weather, the whole landscape can get covered with a thick cover of hail within a few minutes. Hailstones with a diameter of more than 3 cm are not very rare even in Germany. Heavy hail almost only falls in summer. At this season the cumulonimbus clouds can become so mighty that the upcurrent is even able to carry very big hailstones. Sleet is a kind of miniature hail, not bigger than 5 mm. It is white like milk and forms at temperatures around freezing.