Time of Day of Summer Rainfall at
Dodge City, KS
Hourly rainfall observations have been taken here in Dodge City all the way back to the early 1900s! A climatology of summer (June-August) rainfall by time of day for 1907-2011 was developed based on these hourly rain amounts. This climatology represents 105 years of observations and shows the percentage of rainfall occurring during each hour of the day. The time scale at the bottom of the graph is in daylight saving time.
In contrast to the cool season (November-March) when high plains precipitation generally does not depend on the solar cycle, thunderstorm activity with heavy rain in summer is diurnally modulated. In Dodge City, thunderstorm activity is generally at a minimum between 10 am and 2 pm CDT because there is usually a cap (warm layer above the surface that prevents thunderstorms) in place such that strong solar heating is required for storm development. Initial, isolated storm development can occur as early as 2 pm, but usually is delayed to between 3 and 6 pm CDT with peak heating. Even if these isolated storms develop earlier, the chances of them developing overhead are low. Due to the isolated to scattered nature of these afternoon storms, many places may not experience rainfall. However, if the large scale weather pattern is favorable, the isolated storms can occasionally grow upscale into larger storm clusters during the evening, producing widespread rainfall, and peaking between 9 and 10 pm CDT. Sometimes these storm clusters persist well into the night and early morning before gradually weakening or moving into eastern Kansas. Another way that heavy summer rainfall can occur in western Kansas is when afternoon storms develop near the favored topographic features of Colorado and New Mexico (near the Raton Mesa, Palmer Divide and even Laramie Ridge) and then progress eastward or southeastward into western Kansas during the late evening and overnight. This may account for the secondary peak in heavy rainfall shown in the climatology between 12 and 2 am CDT. Therefore, individual storms can develop locally in western Kansas and grow upscale into large clusters, or the initial cells can form in the immediate lee of the Rockies and then progress into western Kansas overnight in the form of larger clusters. After a lull during the late morning and early afternoon, daytime heating is usually required to get the process started again the next afternoon, provided that the large scale weather pattern is still favorable for thunderstorm activity.