Most rain falls during the summer. Sporadic rainfall is throughout the year (in Prague, the average number of days per month experiencing at least  of rain varies from 12 in September and October to 16 in November) but concentrated rainfall (days with more than  per day) are more frequent in the months of May to August (average around two such days per month). Severe thunderstorms, producing damaging straight-line winds, hail, and occasional tornadoes occur, especially during the summer period.