Absolutely, in fact this is more common then most pond owners know. During the summer ponds in Texas generally stratify. This means that the pond water column separates into layers. There is a layer of warm water on the surface, typically high in phytoplankton density, and containing dissolved oxygen. The water on the surface is warmed by sunlight but due to lack of vertical circulation this warm water doesn't mix with deeper water. The water below becomes cooler, has little to no phytoplankton, low oxygen, and poor water quality. Throughout the summer these differences can greatly increase.
Then the big rain comes, the one we are all praying for. This summer rain has a cooler temperature then the surface temperature of the pond. This can cool the pond quickly causing a rapid mixing. The results of the rapid mixing can cause low dissolved oxygen, wide pH fluctuations, and exposure to high ammonia. First the largest fish will die, usually grass carp, bass, and large bluegill. Mid sized baitfish and eventually fry will die if the fish kill persist. Typically this would occur overnight or early morning when oxygen levels are naturally lowest. However, I have seen afternoon hail storms cause the same kills.
Our livestock, wildlife, and families need the water so keep praying for rain and lets hope all our ponds are prepared for its arrival.
Steven Bardin M.S.