Fire district urges valley residents to hold off burning until air is clearer
It’s that time of the year. Winter inversions, a classic Pacific Northwest winter weather phenomenon, occur when a high-pressure ridge traps cold, dense air in the valleys, while warmer, sunnier conditions prevail at higher elevations. These inversions create a “lid” that traps fog, clouds and pollution below, sometimes lasting for weeks on end, bringing cold, grey days to low-lying areas.
While many have enjoyed the sunny afternoons these past several days — when the fog burns off — the murky morning conditions are predicted to dominate in the Illinois Valley until the end of the week.
“There’s been a large area of high pressure over the region for more than 10 days,” explained Marc Spilde, a meteorologist with the National Oceanic and Atmospheric Administration office in Medford. “We’ll likely continue to see this pattern until the weekend, when a weather system coming in from the north will bring a chance for the fog and low clouds to break.”
Spilde also explained how fog pools in the low-lying areas at night and often burns off in the afternoon, but that’s because “the Illinois Valley is narrow and small,” he said.
“The sun is able to erode the fog out that formed overnight — and with this weather pattern lasting this long, many areas have really dried out. However, Grants Pass, being wider and lying 400 feet lower in elevation: that means moisture has more opportunity to pool there. That’s why the dense fog persists there into the afternoons.”
He added that, with little to no wind to mix things up, fog can get trapped in the valleys; while off shore winds at the coast have been clearing those locales out. However, weather throughout the entire region is expected to shift soon.
“Looks like as we head into next week, there is a low probability for some storm systems to come in,” Spilde added, still, another week of dry weather will continue to dominate the inland areas, but the afternoons should be sunnier. “There’s a 20-40 % possibility of rain at the coast.”
Stagnant air conditions have caused poor air quality, which can aggravate some medical conditions — and while there are no legal restrictions on outdoor burning, still, Chief Holmes, with the Illinois Valley Fire District, wants people to hold off on their outdoor burning projects.
“I mean when you can’t hardly see and it’s like pea soup, the smoke doesn’t dissipate,” Holmes said. “The air is so still and the particulates just hang there, so for people who have asthma or COPD, it’s really hard on their respiratory conditions. We do get a lot of medical calls for help during these inversions.”
“Even small burn piles can cause a wide-spread smoke impact while they’re burning, so really, to protect community health, if people don’t need to burn that day, it’d be better for everyone if they wait.”
The IVFD’s new 2025-2026 IVFD Community Connect Burn Permits are now available online at www.ivfire.com. If possible, it’s good to print it out and have the permit available, or keep a copy of the permit on your cell phone.
The freezing fog also causes nighttime hazards and slick morning roads, so Holmes also wants to caution people about driving without headlights. “During the day, with just your daylight running lights, that’s not giving rear lights, and, in this fog, it’s hard to see people coming or going.”
Meteorologists often talk about El Niño or La Niña weather patterns, and a contributing factor to this year’s weather inversion is the La Niña weather pattern that has dominated the region.
With an El Niño weather pattern, warmer waters pool closer to the Pacific Ocean’s surface near the equator off of South America — a result of weakening trade winds — often disrupting normal wind and rainfall patterns globally. This warming persists until an upwelling of colder ocean water mixes with that warmer water, breaking it up, which then results in either a neutral state or a La Niña pattern, essentially the opposite of the El Niño pattern.
The La Niña is thus characterized by cooler-than-average sea surface temperatures in the central or eastern equatorial Pacific, often bringing cooler and drier conditions to dominate the western U.S.; while the western Pacific (Asia, Indonesia, Australia) experiences increased rain and storms.
“We’ve been in a La Niña pattern since sometime in December, so that’s why we’ve been a little drier and a little colder, with storm tracks coming from the north,” Spilde said. “This can bring increased snow, like there was in December, but right now that’s not happening because there’s been this high pressure system in place. That’s also why there’s been so much storminess in the central part of the nation, with cold weather dipping south into the Carolinas and Florida.”