Severe thunderstorms again frequented the state on Tuesday with the Storm Prediction Center issuing two Severe Thunderstorm Watches to cover the activity. The second watch was issued just before 7 PM Tuesday evening. The watch was effective to kill off the thunderstorm activity and the watch was subsequently cancelled around 8:40 PM. The watch duration of just under two hours is the subject of today's daily feature. The chart presents the duration of severe thunderstorm watches for counties within NWS Des Moines's county warning area. The orange line is the accumulated frequency by duration at issuance. The blue line is the accumulated frequency by final watch duration. Watches can be extended in time, so that is why there is a small overlap near the longest durations. The side panel lists out the shortest and longest watches. The two hour duration comes in at about 5%, so about 1 in 20.