Heat, humidity, lightning and fire: Summer in Oregon

EUGENE, Ore. - Hot weather will retain its grip on most of Oregon while Central and Southern Oregon face the risk of new wildfires sparked by lightning.

The National Weather Service issued a heat advisory through at least Tuesday for much of Oregon, with the exception of the Oregon Coast.

In the Willamette Valley, high temperatures this weekend will generally be in the mid 80s to mid 90s.

High temperatures will climb into the upper 80s to upper 90s early next week.

Nightfall may not bring much relief: low temperatures in the upper 50s to near 70 can be expected each night from Saturday night through Wednesday, forecasters said.

And it will become increasingly more humid over the weekend, making it feel warmer than the actual air temperature, forecasters said.

"The hot and relatively humid conditions will be of more concern to the elderly, the infirm and the very young," the Weather Service said in a statement. "Be extra cautious when conducting outdoor activities during the afternoon and evening."

Much of the Southern Oregon Cascades were under a red flag warning Friday as the area weathered storms capable of producing lighting. A red flag warning means conditions are prime for new wildfires to start and rapidly spread.

Thunderstorms with abundant lightning are in forecast for Central Oregon on Sunday.

"Hot and dry conditions, in addition to storms initially starting out with little rainfall, will lead to an enhanced threat of new wildfires," the Weather Service said.

It could be worse: temperatures from Pendleton north into Central Washington are forecast to soar in the 100s next week. Firefighters are already battling widlfires there in hot and dry conditions.