But Mr. Beighle knows it's not the change in seasons that's causing the leaves to fall. A severe drought that has starved fields and lawns of moisture and turned them brown is forcing thousands of trees across Oklahoma to drop their leaves in a desperate effort to survive.
"These trees are going through a summer dormancy," said Mr. Beighle, a nurseryman at TLC Landscape Services in Oklahoma City. "The moisture in the ground is just so dry. They're dropping their leaves to compensate."
In forests and front yards across the state, trees are shedding their leaves weeks before the shorter days and cooler temperatures of autumn would ordinarily begin the process. Autumn begins on Friday.
Many parts of Oklahoma have experienced record summer heat. Some areas, including Oklahoma City, have gone 50 days without measurable precipitation.
"It's the longest stretch without any rainfall," said Chris Sohl, a meteorologist with the National Weather Service in Norman. Another cold front is scheduled to enter the state on Tuesday or Wednesday, bringing cooler temperatures but no rain, Mr. Sohl said.