Climatologists said Thursday that the La Nina conditions that have contributed to Texas' worst drought in decades may re-occur later this year _ troubling news for the state's beleaguered farmers and ranchers who also learned there was likely no relief in sight.

The Climate Prediction Center issued a La Nina watch on Thursday, just two months after declaring the last La Nina had ended. The phenomenon, which is marked by a cooling of the tropical Pacific Ocean, typically results in less rain for southern states.

It was only part of the bad news for Texas, which has been in a prolonged drought along with neighboring Oklahoma and New Mexico: The U.S. Drought Monitor predicted most of the state would remain in "exceptional" drought _ its highest classification _ through the end of October.

"It's a double-whammy of sobering news for Texas," National Weather Service meteorologist Victor Murphy said.

A La Nina watch means conditions are favorable for La Nina to return within the next six months. But it's more likely Texas will know early as October or November, said Mike Halpert, a deputy director of the Climate Prediction Center, which is part of the federal National Oceanic and Atmospheric Administration.

Meteorologists were awaiting confirmation on Thursday that the current drought is the second worst in Texas history, trailing only a devastating drought in the 1950s that was also fueled partly by a series of La Ninas.

In Dallas, where county officials say at least 12 people have died from the heat this summer, high temperatures on Thursday were expected to hit 109 degrees, which would be a record for the date. Experts believe the unrelenting heat will cause record losses in the billions of dollars for Texas ranchers and farmers, while the state's electrical grid has strained all week trying to keep up with unprecedented demand for power.