Shawn Ferreria, Air Quality Expert: "We have a strong high pressure system that has built over the Valley, it's created a lid, it's trapping air pollution, and it's causing our ground level ozone to increase."
Penetrating sun combined with particles like car and truck exhaust, industrial fumes and livestock emissions are key ingredients creating the air hazard.
Light breezes are swirling the air around without dissipating it.
"Basically, what will save us is the high pressure breaking down and allowing for a weather system off the eastern pacific to come into the area and mix things out. Until that happens unfortunately we're underneath this ridge."
This summer it's likely we'll see many unhealthful days especially since new tougher restrictions went into effect.
Starting May 1st EPA guidelines changed from 85 parts per billion to 75 parts per billion over an 8 hour period.
On days when air quality is moderate or worse limiting outdoor activity during the hottest peak hours is recommended.
But there's good news for those staying indoors PG&E says major upgrades in the Fresno area should mean fewer power problems including outages this summer.
"Since 2006, the company has made a very strong commitment to investing in the infrastructure here in the valley because of its growth and because of the heat so we certainly expect to see a reduced number of outages as a result of it."
Power officials say no blackouts are predicted this summer but plenty of gray smoggy air is in the forecast.
Thursday air quality is moderate for most in every Valley county except for Merced and Mariposa. Air quality is expected to deteriorate even more over the next few days as the heat becomes more intense.