In Kentucky, for July to be cooler than normal, there typically has to be a trough over the eastern United States that leads to several cold frontal passages that bring refreshing relief from the typical tropical air mass that resides over the Mid-South during summer. Since cold frontal thunderstorms often have better spatial coverage than convectively produced air mass thunderstorms, it is common for a cooler than normal July to also have normal to above normal precipitation. Not in 2007.
In July 2007 there were three strong cold fronts that moved across Kentucky that helped to keep July temperatures > 1 degree F below normal statewide. While north-central Kentucky, including Louisville (-0.17″) and Lexington (+1.58″), both had normal to above normal precipitation, south-central Kentucky, including Bowling Green, was much drier than normal (-2.51″). In fact, July 2007 was one of only eight Julys since 1900 that featured a temperature departure more than -1 F and a precipitation departure of more than -2″. The last such July was back in 2000. So unlike the cool Julys of 2003 and 2004 (both wetter than normal), July 2007 was truly a rare event.
