CannaGLAP
Grow cannabis in Englewood, CO
Growing cannabis in Englewood: September afternoons near 77°F, nights near 49°F
Late summer in Englewood plays two seasons in one day. September afternoons average about 77°F, then the average night falls to about 49°F, a drop of roughly 28 degrees. Buds are swelling right through it.
The question is not whether your plants can take warm or cold. It is whether your setup can handle both inside the same 24 hours.
Adults 21 and over: yes (residents). Plant limit: 6 per resident, 3 or fewer flowering; 12 per residential property unless local law allows more.
Enclosed, locked area not openly visible; separate locked space if anyone under 21 lives there; local rules can be stricter. Source: Colorado home grow laws; 12 plant cap: HB 17-1220. Local rules (landlords, HOAs, city codes) can add more; this is a summary, not legal advice.
An Englewood tent through the swing
A tent in a spare room off South Broadway or a garage near CityCenter feels that swing unless something buffers it. In September the space may need venting in the afternoon and heat before dawn. A thermostat-controlled heater plus an exhaust fan on its own controller covers both, and running the lights overnight keeps the coldest hours lit and warmer.
Summer leans the other way. July averages about 86°F with roughly 15 days at 90°F or hotter, and August adds about 9 more. Lights overnight from June through August put lamp heat into nights that average 53 to 60°F instead of into the afternoon.
The dry air helps a flower room and hurts a seedling. Humidity averages about 37 percent in July, the driest of the months measured, and about 41 across September and October, so bud rot pressure stays low. Fresh clones and seedlings need a dome or a small humidifier for their first two weeks, and drying buds want a closed space so they do not crisp.
Winter is long. The weather station, 4.5 miles away at 5,610 feet, counts about 147 freezing days a year, and January lows average about 19°F even with afternoons near 46°F. January's 67 percent outdoor humidity means little in a heated house, which runs dry, so skip the winter dehumidifier unless the tent sits in a cold, damp basement.
Heater safety: use one with tip-over and overheat shutoff, plug it straight into a wall outlet (not an extension cord or power strip), and keep it a few feet from tent fabric and plants.
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 46 | 47 | 55 | 60 | 69 | 81 | 86 | 85 | 77 | 64 | 53 | 45 |
| Avg low °F | 19 | 20 | 28 | 35 | 44 | 53 | 60 | 58 | 49 | 37 | 28 | 20 |
| Humidity % | 67 | 40 | 37 | 44 | 40 | 41 |
Highs and lows: NOAA 1991 to 2020 normals, Marston Fltr Plt station (4.5 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.
Outdoors in Arapahoe County
Colorado home growing is for residents: up to 6 plants each, no more than 3 of them flowering, and 12 per residential property unless local law allows more. Every plant must sit in an enclosed, locked area that is not openly visible, with a separate locked space if anyone under 21 lives in the home, and local rules can be stricter than the state's.
If you have that space, start seeds April 7 to 21 and set plants out May 19 or later. Frost usually ends around May 2, but nights average 45°F only from May 19. Warm 50°F nights run from about June 5 to September 11, the average night drops below 45°F after September 25, and the early first frost can arrive by September 27. That is about 131 days, so choose autoflowers or photoperiods that finish by mid September.
| Last spring frost | May 2 in a typical year, May 17 to be safe (later only 1 year in 10) |
|---|---|
| First fall frost | Oct 11 typical, as early as Sep 27 (1 year in 10) |
| Frost-free season | about 160 days |
| Nights stay 50°F or warmer | Jun 5 to Sep 11 |
| Start seeds or clones indoors | Apr 7 to Apr 21 |
| Move plants outdoors | May 19 or later |
| Season note | Frost can arrive before mid October here: long flowering plants may not finish outdoors |
An Englewood grow that stays yours
Englewood is compact. Between the shops on South Broadway, nights at the Gothic Theatre and visits to the Museum of Outdoor Arts, you see the same faces often. A small grow is easy to keep out of sight, and your records deserve the same discretion: the dates that beat a September 27 frost took a season to learn.
Canna GLAP encrypts your grow journal on your phone before upload. A break-in at our servers would net the intruder grow records in locked form, with no key to read them. What you learned about the September swing stays in your hands.
What is encrypted: your plants, notes, photos, feed logs and harvests. What is not: account details (such as your email, name and plan), a grow name or town if you type one, your team, and your sensors' names. The full list: what a hacker would get.
Questions growers in Englewood ask
When should I plant cannabis outside in Englewood?
May 19 or later, from seeds started April 7 to 21. Frost usually ends near May 2, but nights stay below an average of 45°F until May 19.
How long is the outdoor cannabis season in Englewood?
About 131 days, from May 19 to an early first frost on September 27. The typical first frost comes around October 11, but plants that finish by mid September are the safer bet.
Is Englewood's air too dry for cannabis?
For seedlings and clones it can be, since July averages about 37 percent humidity. For flowering plants it is an asset: September and October average about 41 percent, which keeps bud rot pressure low.
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