It doesn’t take living in Colorado long to observe the extreme fickleness ofr the weather. 75 degrees in January? Sure! Snow in July? Why not. It’s no wonder, then, that many Coloradoans are still unsure when the best time is to winterize their pool. Like so many things, weather variations differ widely according to the exact geographic location of your in-ground pool. The pool season in Grand Junction or Dillon is not the same as the pool season in Denver. Local environmental pressures can alter local pool seasons dramatically from one region to the next.

Clearly, most of us realize there are limitations to pool season here in the Centennial State, but it’s only natural to want to hold on to your pool time until the very last possible day. While we’re not able to give exact days or dates to close your pool, historical weather data can, at the very least, get us in the ballpark.

In this study, we will be comparing the 5-year historical temperature data of three Weather Underground weather stations in the state of Colorado hailing from three very different environmental regions: The Front Range (Denver), The Rocky Mountains (Dillon). and The Western Slope (Grand Junction). Hopefully, after studying these regions you will have a better idea whether or not extending your pool season just that little bit longer is really a good call when it comes to the longevity and usability of your pool.

Determining Data

The first and final frosts of each year are the unofficial indicators of pool season. In light of this, for this study we will set the benchmark of ‘pool season’ for the time of the year that exhibits daily low temperatures at 60+F. However, it would be inconsequential to look only at only one or two years’ first and final frosts to attempt to set an exact date of when to open your pool for the upcoming Summer and winterize your pool for the upcoming Winter.  Pool and Spa Experts turns back time a bit further, using the 5-year historical data of each of the 5 regions to give a regional ‘average pool season’.

All data has been accrued from the Historical Weather page on the Weather Underground website.

When to Winterize You Pool – Denver, CO

Nicely nestled next to the foothills of the Rocky Mountains, Denver experiences large swings in temperature thanks to its locale – sometimes even multiple times in one day. For this reason, predicting your pool season is tricky in the Mile High City. Some years see a nearly 5 month pool season(YEAR), while others are cut short at 3-4 months (YEAR).

when to winterize your pool denverdenver-2012-13weather-d-2013-14d-weather-2014-15
d-weather-15-16Average Pool Season: June-Sept (4 mo)
Recommended Winterization: 2nd week of September

When to Winterize You Pool – Dillon, CO

Unlike its fellow D-town big brother, Dillon, Colorado, located in the heart of the Rocky Mountains on Interstate 70, typically observes a short pool season of only ~2-3 mos consistently throughout the years studied. The elevation and sun angle play a large role in the shortened pool season in this region. Makes sense – tall mountains provide LOTS of shade. So much so that many areas in the region experience snow melt well into late June and early July – not ideal for poolside relaxing.



historical temp data dillon co


when to winterize your pool dillon historical data

Average Pool Season: July-August
Recommended Winterization: 1st Septemeber

When to Winterize You Pool – Grand Junction, CO

You may be shocked to know that the average monthly temperature in Grand Junction is nearly 10 degrees higher than the Mile High City of Denver any given month of the year. Because of this, Grand Junction experiences a typically longer pool season than any of the other regions presented in this study. According to the data presented below, the average pool season in Grand Junction runs 5+ months, solidly. You may be driving through snow in the mountains along I 70 only to emerge in a temperate zone 20-30 degrees hotter (!!!) when descending into Grand Junction.




Average Pool Season: mid-May to mid-Oct
Recommended Winterization: 2nd week Oct

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