When is the first freeze in Lone Tree?
In half of years the first fall freeze reaches the Lone Tree area by October 8, and in one year out of ten it arrives by September 25. Those are NOAA’s 1991 to 2020 climate normals for Denver Centennial Airport, the official station a few miles northeast of Lone Tree.
Atlas Mechanical LLC is a family-owned HVAC and plumbing company in Lone Tree, Colorado, run by owner and lead technician Jared Bigham, serving 19 cities across the south Denver metro.
First and last freeze dates around Lone Tree
NOAA publishes freeze probabilities for every long-running weather station. Four of them sit around Lone Tree: Denver Centennial Airport to the northeast, Cherry Creek Dam to the north, Parker to the east and Castle Rock to the south. The table reads like this: at Centennial Airport, one year in ten has its first freeze by September 25, half of years by October 8, and nine years in ten by October 20.
| NOAA station | 1 year in 10, freeze by | Median first freeze | 9 years in 10, freeze by | Median last spring freeze | Median freeze-free days | Nights at 32°F or below, per year | Nights at 0°F or below, per year |
|---|---|---|---|---|---|---|---|
| Denver Centennial Airport | Sep 25 | Oct 8 | Oct 20 | May 5 | 154 | 155 | 5 |
| Cherry Creek Dam | Sep 25 | Oct 8 | Oct 19 | May 7 | 152 | 172 | 6 |
| Parker | Sep 21 | Oct 3 | Oct 15 | May 9 | 145 | 177 | 10 |
| Castle Rock | Sep 17 | Oct 2 | Oct 16 | May 9 | 143 | 167 | 7 |
Source: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991 to 2020 (stations USW00093067, USC00051547, USC00056323, USC00051401), pulled October 31, 2026. A freeze here means a low of 32°F or colder. Night counts are rounded averages.
The south end freezes first. Castle Rock and Parker reach their median first freeze about a week before Centennial Airport, and Parker averages roughly twice as many nights at or below zero (10 a year against 5).
How fast heating demand climbs after the first freeze
Heating degree days are the standard measure of how hard a heating system has to work. At Centennial Airport the 1991 to 2020 normal is 6,014 a year. October averages 468, November 771 and December 1,041, so the load more than doubles between October and December. December and January together carry about 34 percent of the whole year’s heating demand, and October through April carries about 92 percent (NOAA monthly normals, same station and period).
That shape is why the first cold nights produce a burst of no-heat calls. A furnace that coasted through September in short cycles is suddenly asked to run long, back-to-back cycles, and a part that was already weak fails then. Why furnaces quit on the first cold night →
What the dates mean for your furnace
Book the check before the first freeze, not after it. With a one-in-ten chance of a freeze by September 25 at Centennial Airport and by September 17 in Castle Rock, late September is the window that covers most years. What a furnace tune-up includes →
Plan for May, not April. The median last spring freeze is May 5 at Centennial Airport and around May 9 in Parker and Castle Rock, so heat is still needed well into spring.
If the heat is already out, we work across Lone Tree, Highlands Ranch, Castle Rock, Parker and the rest of the south metro, evenings till 9 PM. Furnace repair →
Common questions
When is the first freeze in Lone Tree, Colorado?
Does the first freeze come earlier in Castle Rock and Parker?
How many freezing nights does the south Denver metro get in a year?
When should I get my furnace checked in Lone Tree?
When is the last spring freeze in Lone Tree?
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