FRESNO, Calif. (KGPE) – Hazy skies blanketed the Central Valley Friday, leading to unhealthy air quality and leaving people wondering if wildfire smoke was to blame.

But experts said poor air quality is common this time of year with high levels of the potentially dangerous very fine particulate matter pm 2.5.

“Particulate matter pollution is microscopic. It’s teeny tiny particles that you can inhale and it’s not good for your health. Because they’re so small you breathe them in and they get into your bloodstream,” Heather Heinks the outreach and communications manager for the Valley Air District said.

Some Woodward Park visitors like Wyatt Seaman noticed the poor air quality instantly.

“I was planting pistachios. I’m always outside and I have asthma. So, I mean smoke is never good for people with asthma,” he said.

Others like Edge Dostal said everything seemed clear.

“We come out and play disc golf, my wife and I, almost every day either here or at Kearney Park and there have been a lot of smoky days this summer and after the rain it’s been beautiful. I didn’t notice anything really today,” he said.

The Valley Air District said because overnight temperatures dip this time of year, more people are using their wood-burning fireplaces, so many throughout the Valley may be waking up to the smell of smoke.

Experts also said air gets stagnant in the cooler months and lingering smoke from wildfires and other particulates could be getting trapped on the Valley floor.

“We see this weather that really holds all that pollution low to the ground and really creates these environments where it is unhealthy at times for residents to be breathing that air,” Samir Sheikh with San Joaquin Valley Air Pollution Control District said.

Starting Nov. 1 people are strongly encouraged not to burn in their fireplaces to reduce air pollution both inside and out.

There are grants available for anyone with wood stoves or fireplaces to convert them to gas or electric.