CannaGLAP
Grow cannabis in San Luis, AZ
Growing cannabis in San Luis: a September that is still full summer
San Luis takes its long weather record from the Yuma MCAS station, 14.8 miles away and 213 feet up. September averages 101°F in the afternoon, with about 29 days reaching 90°F and nights near 78. October still gets about 19 of those days.
On a calendar, September looks like the end of summer. Here it is when buds fill out in heat that has run since May. Which one is your grow planned around?
Adults 21 and over: yes. Plant limit: 6 per adult at primary residence; 12 per residence with 2+ adults.
Enclosed area with a lock that keeps minors out; not visible from public view. Source: A.R.S. 36-2852. Local rules (landlords, HOAs, city codes) can add more; this is a summary, not legal advice.
Cooling a San Luis tent from May to October
The heat run is long. From May through October, each month averages 18 or more days at 90°F, and June through September each top 28. July and August highs average about 107 and 106°F, and nights hold near 83. A tent in a garage or spare room needs real cooling here, a room air conditioner or exhaust into a cooled space, because from June to September even the average night bottoms out at about 75°F or warmer. Overnight lights still help, since 83 beats 107, but they are no substitute.
The air is the other half. Humidity measured about 29 percent in June and 28 in September, lower than any other month measured. Seedlings and fresh clones lose water faster than young roots can replace it, so give them a dome or a small humidifier for their first two weeks.
Harvest is where the dryness bites. Buds cut in September or October and hung in air near 28 to 30 percent can dry in a few days and smell like hay. Dry them in a closed tent or closet in the coolest room you have, and stretch the dry to a week or longer.
Winter is the easy stretch. December and January afternoons average about 68 and 70°F, freezing nights almost never happen, and nights dip below 50°F on average only from about December 3 to February 11. A tent needs no heater, and January's 53 percent is the dampest of the months measured.
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 | 70 | 73 | 80 | 86 | 94 | 103 | 107 | 106 | 101 | 90 | 78 | 68 |
| Avg low °F | 48 | 50 | 55 | 60 | 67 | 75 | 83 | 83 | 78 | 66 | 54 | 47 |
| Humidity % | 53 | 29 | 34 | 32 | 28 | 30 |
Highs and lows: NOAA 1991 to 2020 normals, Yuma Mcas station (14.8 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.
Outdoor timing near the border
Arizona allows 6 plants per adult at a primary residence, or 12 where two or more adults live. The plants must sit in an enclosed area, locked so minors cannot get in, and not visible from public view. A locked greenhouse could fit if no one can see into it from public view.
Frost is not the limit here; heat is. Sow indoors from March 4 to 18 and plant out on April 15 or later, so young plants meet May's roughly 24 days at 90°F with time to settle. Plants that flower in September do it at 101°F, so lean toward heat-tolerant strains, and expect the easier finish in October and November as highs ease to about 90 and then 78°F.
| Frost | Rare: less than 1 freezing night a year on average |
|---|---|
| Nights stay 50°F or warmer | Feb 11 to Dec 3 |
| Start seeds or clones indoors | Mar 4 to Mar 18 |
| Move plants outdoors | Apr 15 or later |
Keeping a border-town grow to yourself
San Luis sits right on the U.S. Mexico border, and much of the local market scene runs through the weekend markets in nearby Yuma. A grower who learns how to finish buds in a 101°F September has notes worth guarding, whether from a relative, a roommate, or another grower down the road chasing the same strains.
Canna GLAP locks the grow log itself on the phone before anything is uploaded. If our servers were ever broken into, the thief would get encrypted grow records and nothing that opens them. The cooling and drying settings you worked out stay on your side of the line.
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 San Luis ask
When should I plant cannabis outside in San Luis, Arizona?
April 15 or later, with seeds started March 4 to 18. Frost is almost never a concern, so the date is about giving plants a few weeks before May's heat, which averages about 24 days at 90°F.
Does it ever freeze in San Luis?
Almost never. The Yuma MCAS record averages about 0.1 freezing days a year, and average nights stay above 45°F in every month.
Why do my buds dry so fast after harvest in San Luis?
The air at harvest is very dry: September measured about 28 percent humidity and October about 30. Dry in a closed space and slow it down to a week or more.
Growing near San Luis
- Grow cannabis in Yuma, AZ 17 miles
- Grow cannabis in Coachella, CA 115 miles
- Grow cannabis in Indio, CA 119 miles
- Grow cannabis in La Quinta, CA 120 miles
- Grow cannabis in Palm Desert, CA 126 miles
All Arizona cities · Every state where adults may grow at home