Denver spent the weekend under an Ozone Action Day, the kind of flat, hazy sky that makes the foothills look like a rumor. It is not fireplace weather. But the two things that will decide what your chimney costs you this winter both moved in the last two weeks: NOAA raised its confidence on a very strong El Nino, and the state's new wildfire insurance law started generating real paperwork for real homeowners. Here is what changed, and what it means once the first hard freeze comes down off the Front Range.
Metro Denver is under an Ozone Action Day right now
The Colorado Department of Public Health and Environment and the Regional Air Quality Council issued an Ozone Action Day Alert on July 19 for the Front Range Urban Corridor, from Douglas County north through Larimer and Weld, including Denver, Boulder, Fort Collins and Greeley. It runs until at least 4 p.m. Monday, July 20, with ozone expected in the Unhealthy for Sensitive Groups range through the afternoon and evening. You can check the live status any time at colorado.gov/airquality.
Open burning is prohibited while an Action Day is in effect. In July that means the fire pit and the slash pile, not your fireplace. But the same Action Day machinery is what governs your wood stove starting November 1, when the winter high pollution season opens and the restrictions switch from outdoor burning to indoor burning. CDPHE spells out exactly who is covered and who is not:
"During an air quality Action Day, indoor burning is restricted in the seven metro Denver counties: Denver. Boulder. Broomfield. Douglas. Jefferson. Areas west of Kiowa Creek in Adams and Arapahoe counties. Exemptions: A wood burning device is exempt from burning restrictions if any of the following are true: Device is on a list of certified or approved indoor burning equipment: Phase II EPA-certified stoves. EPA-certified pellet stoves. Colorado-approved masonry heaters. Device is located above 7,000 feet."
What this means for your home: if you live below 7,000 feet in those counties and your firebox is an open masonry fireplace or an old uncertified stove, you are on the restricted list every Action Day from November through March. That is a reason to know now, in July, whether your device is on the approved list. We laid out the full picture in our guide to Colorado chimney laws and regulations, and a gas insert sidesteps the restriction entirely if you are tired of watching the advisory page.
NOAA just raised the bar on this winter: very strong El Nino
Two weeks ago the forecast was "El Nino is here." Now it is louder. In its July 9, 2026 ENSO Diagnostic Discussion, the NOAA Climate Prediction Center kept the El Nino Advisory active and put a number on it:
"El Nino continues and will strengthen through the end of the year, with a 97% chance it will persist through early spring 2027."
Source: NOAA Climate Prediction Center, ENSO Diagnostic Discussion, July 9, 2026
CPC also puts an 81% probability on El Nino reaching very strong intensity during October through December. That is a high number this far out.
What this means for your home: a strong El Nino does not promise Denver gets buried. It tilts the odds toward a more active southern storm track, and when that track lines up with Front Range upslope, we get the wet, heavy, multi-day storms that pile snow on Palmer Divide and soak masonry from Golden to Castle Rock. For a chimney, water is the whole story:
- Freeze-thaw. Wet brick that freezes overnight and thaws by noon is how Colorado spalls mortar joints. We see more of it after wet winters than cold ones.
- Crown and cap. A hairline crack in the crown is invisible in July and a leak in February. A missing or rusted chimney cap lets snowmelt straight down the flue.
- Draft. Cold, dense air sitting in an exterior chimney is the classic reason a fire smokes back into the room on the first freezing night of the year.
- Timing. The week after the first storm is the worst week to call anyone in this trade. Book a chimney inspection in Denver while the roof is dry and you can still get on it.
The Xcel rate case is still open, and it changes your heating math
Xcel Energy asked the Colorado Public Utilities Commission for roughly a 9.9% electric increase, about $9.94 a month for the average residential customer, telling Denver7 it needs to recover transmission, distribution and generation investments. As of the Colorado Sun's July 7 reporting, the package on the table is $225 million in new revenue, which would add about $6 a month and take the average bill from $104.68 to roughly $111. The Office of Utility Consumer Advocate and Energy Outreach Colorado are pushing on whether the bill assistance attached to it is anywhere near enough. The PUC has not issued a final decision.
What this means for your home: every dollar on the utility bill makes the fireplace look better as a heat source, and that is exactly when people burn a chimney that has not been swept in four years. If you are planning to lean on the fireplace harder this winter to shave the bill, that is a fine plan, but only with a clean, lined, drafting flue. A dirty flue is not a cost saving, it is a deferred bill. A sweep and cleaning costs less than one month of the difference these rate cases are arguing over.
HB25-1182 is live, and the notices are starting to land
The state's wildfire risk model law took effect July 1. Under HB25-1182, an insurer that uses a wildfire risk model, catastrophe model or risk score to underwrite, price, non-renew or surcharge a Colorado homeowners policy has to tell you about it. That means a written annual notice with your wildfire risk score or classification, the range of scores a property can get, what mitigation actions would move it, and how to appeal. If the insurer does not build property-level and community-level mitigation into its model, it has to give discounts to policyholders who can show the work they have done. Appeals go to the insurer, and the insurer has to acknowledge receipt in writing within 10 calendar days.
What this means for your home: read the notice when it shows up instead of filing it. If your score looks wrong, you can appeal it with evidence, and documented work counts as evidence. Chimney work is a real piece of that file. A spark arrestor cap on the flue is a standard ember-ignition control, and it is one of the few mitigation items that is cheap, permanent and photographable. Keep the invoice and the inspection report. Colorado's wildfire mitigation tax credit also remains available through tax year 2027 for out-of-pocket mitigation done by a third-party provider, so the same paperwork can do double duty.
What we would do before the next edition
- Look up your wood stove or insert and confirm whether it is Phase II EPA-certified, an EPA-certified pellet stove, or a Colorado-approved masonry heater. If it is none of those and you are below 7,000 feet in the seven metro counties, plan around November 1.
- Get eyes on the crown and cap before the first storm. Cracked crown, rusted cap and missing spark arrestor are the three we find most often in July and the three that cost the most in February.
- Book the inspection now, not after the first cold snap. A wet, El Nino-leaning winter means everyone calls at once.
- Open the insurance notice when it arrives, check the wildfire score, and start a folder for mitigation receipts.
- Test the CO alarms. If you are burning more to offset a higher electric bill, that alarm is the cheapest safety device in the house.
If you want a straight answer about what your chimney actually needs before winter, call us at (720) 207-9232 or reach out through our contact page. We serve Denver and the Colorado Front Range, and we will tell you when something can wait.
The Flue Report is published every two weeks by Adam Chimney Sweep, serving Denver and the Colorado Front Range. Edition 3 lands the week of August 3, 2026.
