An interruption is an unscheduled break in play and can be caused by all manner of things - rain, bad light, streakers, riots, bomb scares, even fog and snow - you name it and it has probably happened somewhere. If the interruption occurs during the Last hour of the match there is a formula to work out the number of overs lost. Many limited-overs matches and competitions employ the Duckworth-Lewis method to recalculate required totals in matches that have suffered interruptions or late starts.