by: Jake Dickman* | June 10, 2026

It's that time of year: watch the hillsides shift from verdant green to sepia tan, and you know what that means for our golden state. Fire season has arrived. With it comes a host of environmental risk factors that matter as much for wildfire response as they do for your personal safety this summer.

Below are three risk factors that affect both wildfire behavior and heat illness. This isn't a comprehensive overview of either; it's a framework for thinking about these risks in shared context.

For a comprehensive overview of heat illness, visit: PRISM Heat Illness Resource Page For more on wildfire prevention, visit: Cal FIRE Prevention Resource Page.

Risk Factor #1 – High Ambient Temperature

This one is basic: it's hot. For your body, every task carries an increased heat burden, reducing your ability to cool yourself and depleting fluids more rapidly. Apply that same factor to terrain and ignition potential rises with the thermometer. Both risks spike during heat waves.

Risk Factor #2 – Direct Solar Radiation

It's hotter in the sun than in the shade, and that matters in two directions. Sun exposure adds to your body's core temperature load while it pre-heats fuels like dried grass, leaf litter, and fine "elevator fuels" (the dry material that carries a flame from the ground up into the tree canopy or roofline).

That combination is exactly why you'll see signs in Butte County requiring that mowing, weed-whacking, grinding, and other spark-producing activities be completed before 10 a.m. We recommend agencies apply the same logic to scheduling staff: save the most intense outdoor work for the early morning hours.

Risk Factor #3 – Low Relative Humidity

"At least it's a dry heat." We've all heard it, and there's truth to it. Low humidity means shade offers real relief. But there's a catch.

When relative humidity dips below 30%, sweat evaporates so quickly that you often don't notice how much fluid you're losing, and it's gone before it can cool you down. Now apply that to the landscape: California's grasses have been "curing" (losing moisture) all summer and will ignite without much provocation. Layer in the daily humidity swing, and the hours between 1:00 p.m. and 4:00 p.m. consistently mark the highest-risk window for both heat illness and fire.

How to Prepare?

Start by drinking plenty of water, and while you're at it, refresh every supervisor, staff member, and volunteer on your Heat Illness Prevention Plan. It's also a good time to review the Emergency Action Plan, since effective emergency response is an integral part of any Heat Illness Prevention Plan.

As you revisit these policies, remember: they're only as good as the frequency with which you train on them. That training also needs to be site-specific, meaning it addresses the unique risk factors of your public entity and its working environments. For help getting your team up to speed, we recommend managers and supervisors register for our Heat Illness Prevention Webinar to learn the ins and outs of equipping your team effectively. Our "Introduction to Safety" training goes even further, covering not only Heat Illness Prevention but also the IIPP framework it sits within, along with the Workplace Violence Prevention Plan.

As always, if you have any questions or need of assistance, start by reaching out to memberservices@gsrma.org.

* edited with AI