I took these photos of a quick storm that passed just south of the reservoir this weekend.
That same weekend, an overnight storm in a neighboring county brought warnings for heat bursts. From Wikipedia:
A heat burst is a rare atmospheric phenomenon characterized by gusty winds and a rapid increase in temperature and decrease in dew point. Heat bursts typically occur during night-time and are associated with decaying thunderstorms.
While this phenomenon is not fully understood, it is theorized that the event is caused when rain evaporates into a parcel of cold dry air high in the atmosphere making the air more dense than its surroundings. The parcel descends rapidly, warming due to compression, overshoots its equilibrium level and reaches the surface, similar to a downburst.
Recorded temperatures during heat bursts have reached well above 90 °F, sometimes rising by 20 °F or more within only a few minutes. More extreme events have also been documented, where temperatures have been reported to exceed 130 °F, although such extreme events have never been officially verified.
Heat bursts are also characterized by extremely dry air and are sometimes associated with very strong, even damaging, winds.
Smith Family Weblog 
Posted by Rebecca's Mom on July 10, 2008 at 11:17 pm
You should have been here on Monday evening . . .Katie definitely got her wish to see a fantastic Nebraska thunderstorm!
We stopped picking cherries when the little boat that Dave had hanging on a deck post to dry “sailed” across the deck due to a wind shift and “battened down the hatches.” We had 2-1/2″ of rain in about 20 minutes with lots of thunder and lightning.
It was quite a sight watching the storm move across the lake. No more heat bursts, but we’ve had spectacular light shows across the lake every night this week.