Tag: Fire

TUCSON, Ariz. (13 News) – An incoming storm is going to bring much-needed relief to fire risk here in southern Arizona.

It comes after weeks of no rain and even a Red Flag Warning over the weekend.

13 News talked to K.P. Maxwell, Wildland Coordinator with the Tucson Fire Department.

He said wind and relative humidity are the two biggest things he keeps in mind when fighting a wildfire. But he’s much less concerned about wind when humidity is high.

“If we have a moist environment and the fuels have moisture in them, even with the wind on it, it’s going to be hard to get them to burn,” Maxwell said.

He adds that increased humidity impacts some plants more than others.

“Something that’s a fine fuel, like a grass, we call that a one-hour fuel and that grass can absorb humidity from the environment in as little as an hour,” he said. “So if it’s moist outside, the grass within an hour will become moist.”

He also said the opposite is true, with those same fine fuels able to dry out in an hour. That’s one of the reasons 13 First Alert Chief Meteorologist Erin Christensen said humidity is important to keep track of.

“That can give us an idea of when we have the possibility of some rain,” said Christensen. “If the air molecules are really huge because the air temperature is high, they’re going to hold onto that water before they actually drop it in the form of rain.”

And if we don’t have humidity, we get things like Red Flag Warnings which we had last weekend.

“Relative humidity 15% or lower average daily relative humidity. Wind sustained at 25 miles per hour, frequent gusts at 25 miles per hour, and both of those for several hours at a time which brings on a high fire danger rating.”

Maxwell told 13 News his comfort zone is 20%.

“Here in the desert, humidities below 20% can lead to some pretty strong, rapid fire growth,” he said. “But the really fine fuels like the grasses, when we start getting above 20%, it makes them a little less susceptible to burn.”

Maxwell also stressed the importance of creating space around your home as embers can lead to your home igniting. This area closest to your home is called the Home Ignition Zone and it includes things like grass, tumbleweeds, or even leaves in your gutter.

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