FRESNO, Calif. (KFSN) -- A thick layer of fog made driving very difficult in parts of the Valley late Tuesday, while the smell of smoke had people wondering if there was a large fire in the area.
Officials with the San Joaquin Valley Air Pollution Control District say the extreme conditions were caused by a high-pressure system that trapped pollution from cars, residential fireplaces, and agriculture burns over the Valley.
By the evening hours, the particulate matter measurement spiked above Level 5, which is considered unhealthy for everyone.
"Because there was that high-pressure system, that pollution has nowhere to go so it acted like a lid and kept everything at ground level. Plus we had fog so it compiled and it looked horrible yesterday," said Outreach and Communications Representative Cassandra Melching.
Melching said the district has its own team of meteorologists who expected the system to lift much earlier in the day than it did.
"We had anticipated that the system would rise, and we would get that dispersion a lot earlier and it wasn't supposed to impact the Valley the way it did."
Melching said the district tries to protect the public by only allowing ag burning on days when the weather conditions make it safe. Farmers must call in the morning to get approval, but first they go through a lengthy permitting process.
"Weeks in advance a farmer will come to us and let us know what they have. We'll send an inspector out, and there are certain criteria for the things they can burn and the wood has to be completely dry so some of the stuff, new orchards that are ripped up it takes 6 weeks before they can even ignite those."
Officials say they approved residential and agriculture burning because their experts expected the high-pressure system to lift much earlier in the day. Instead, it stuck around and trapped smoky, polluted air for hours.
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Kevin Hamilton with the district's citizen advisory committee says that's also a reason the district won't get fined.
"If they state it's a burn day, and someone had a permit to burn, that's legal. A mistake was made. I think they need to refine their process, using the weather as a tool is risky."
District officials said they usually send out alerts for situations, such as a wildfire, that will impact air over several days.
For a case like this, they didn't send out an alert because they wanted folks to see the latest information on their app or website.
"We were encouraging people to follow the charts, that's the most accurate information, its real-time information," said Jaime Holt from the district.
Steve Johnson, a meteorologist for agriculture, said that's not enough.
"How much of the general public uses their app? Nobody. I don't even use it and I'm a meteorologist. A small percentage of the public uses their app - what about the elderly?" he said.
"The taxpayers are paying you to warn them about stuff like this. You're not doing your job," he added.
Johnson said he spent hours on the phone on Wednesday trying to get an answer from the district.
"After tracing down dozens of calls, I finally got someone that said we goofed, we dropped the ball."
He says he's filed a complaint with the state on the district and hopes next time, folks won't be left in the dark.
Hamilton says they are working with the district in a new plan for cleaner air which will hopefully include a better policy on burn days, and an improved messaging system.
For day-to-day spikes in pollution, the San Joaquin Valley Air Pollution Control District encourages residents to check the Real Time Air Advisory Network online at myRAAN.com or download the app by searching "Valley Air' in the app store or Google Play.