By Heather Brown

MINNEAPOLIS (WCCO) — There are nearly 20 large fires raging across California tonight and it could take weeks to put them out.

You’ve likely seen these big planes dropping something red to fight the flames.

Crews are building fire lines on the ground and dumping millions of gallons of retardant from the air.

The DNR’s Casy McCoy explains the retardant is essentially a mixture of water and fertilizer. It coats the fuels on the ground, depriving them of oxygen so they don’t burn as well.

“It’s going to allow the plant materials to hold that moisture longer than they would with just straight water. The idea is to slow the fire down–it does not put it out,” McCoy said.

The government has found that in rare cases it can be toxic to aquatic species and affect water quality, so aerial retardants aren’t allowed within 300 feet of water.

McCoy says we do use that kind of retardant in Minnesota, but not in the Boundary Waters fires. There was too much water nearby. Instead, planes scooped and dumped water on those flames.

To offer some perspective, the 2011 Boundary Waters fire grew to 145 square miles. The largest one burning now in California is 470. That fire would cover almost the entire metro–from Woodbury to Minnetonka.

The Minnesota Pollution Control Agency says the California smoke likely won’t get to Minnesota. It’s too hard to cross the Rockies and Sierra Nevada.

But the colorful sunsets in the Twin Cities over the past few days? That’s smoke from the fires in British Columbia.

McCoy said at last count, there were about 200 firefighters helping tame wildfires out West.

Heather Brown