These cool summer days were just too good to last.

A low-pressure system that has kept temperatures in the low 90s is lifting, causing the mercury to reach triple digits Thursday, according to the National Weather Service.

Today's high is forecast to be 97 degrees, up from the forecast of 92 on Tuesday.

Normal triple-digit temperatures are expected Thursday, with a predicted high of 101 degrees. 

"We've been experiencing a weird weather pattern for this time of year," said Mike Paddock, meteorologist with NWS in Phoenix. 

The almost chilly June evenings were a result of a low-pressure system hovering over the western states, suppressing the normal high pressure that brings the hotter temperatures, Paddock said.

"But that low-pressure system is weakening," he added. And the high pressure that is building is predicted to "stay anchored" over the area, beginning a warming trend. Paddock forecasts that temperatures will stay in the triple digits through this weekend and into next week.