Triple-digit temperatures could hit the Rogue Valley today, but thunderstorms on the heels of the heat wave have forecasters worried about increasing fire danger.

Triple-digit temperatures could hit the Rogue Valley today, but thunderstorms on the heels of the heat wave have forecasters worried about increasing fire danger.

The National Weather Service's Medford office posted a fire weather watch and a special weather statement Thursday afternoon warning that the combination could bring "critical fire weather conditions" over the weekend.

A weather system sweeping in from offshore will boost valley temper-atures across Southern Oregon today, a National Weather Service forecast reported. Medford's high temperature today is predicted to be 95 or higher, closing in on the day's record of 100 set in 2003. Saturday will just as hot, with 99 forecast for Medford.

But the high temperatures aren't the only thing making forest managers and firefighters sweat.

Hot, moist air from Mexico, known as a "monsoonal push," is now moving across Arizona and Nevada and likely will roll into this region from the southwest on Saturday, said National Weather Service meteorologist Mike Johnson. The monsoonal air usually pushes into the region in July and August.

"Things are setting up optimally for thunderstorm development," he said. "This looks like a big event."

The moist, unstable air brings prime conditions for forming thunderstorms. They'll shape up first in Northern California, already hammered by a lightning storm last weekend, then flow right into Southern Oregon.

"We certainly will get lightning in Medford," Johnson said.

The storms will build through the day Saturday, then continue and become wetter Sunday, delivering heavy rains to some areas. Scattered downpours could cause localized flooding, especially in the mountains, Johnson said.

Although the predicted rash of lightning strikes could spark fires, and prompted the watch for through the weekend, wildlands in Oregon aren't as dry as those in California, he said.

A chance of rain will remain Monday, as temperatures drop back to the mid to low 90s in the Rogue Valley.

Reach reporter Anita Burke at 776-4485, or e-mail aburke@mailtribune.com.