Yellowstone park's Boiling River running warmer

GARDINER (AP) – The temperature of the Boiling River in Yellowstone National Park has been increasing slightly since last August.

In August, the temperature of the thermally heated water at the popular swimming hole north of Mammoth Hot Springs was approximately 134 degrees Fahrenheit. Over the past seven days, the temperature has ranged from about 136.5 to 139.5 degrees.

Park geologist Henry Heasler tells the Livingston Enterprise that he and his staff aren't absolutely certain what's going on.

One theory is cold water flowing into the Boiling River through underground sinkholes in the underlying travertine is being blocked or diverted somehow.

Another theory could be that less cold water from the Gardner River is diluting the Boiling River water where the two rivers meet.