Grow cannabis in San Dimas, CA

Growing cannabis in San Dimas: harvest air that can dry buds too fast

In San Dimas, the trickiest weeks of a run can come after the plants are cut. Against the foothills at the eastern edge of the San Gabriel Valley, October 2024 averaged 44 percent humidity, the lowest of the months shown, while afternoons still averaged about 81°F.

Warm, dry air pulls water from a hanging branch quickly, and a rushed dry can leave buds harsh and grassy. So the question is not only how you grow it. Where will it dry?

California home grow rules (as of October 2026)

Adults 21 and over: yes. Plant limit: 6 living plants per private residence, however many adults live there.

Locked space, not visible from a public place; cities and counties can set reasonable rules for indoor grows (but cannot ban them) and may ban outdoor grows; a landlord may prohibit growing on a rental. Source: Department of Cannabis Control; conditions: Prop 64 text as passed in 2016 (H&S Code 11362.2 and 11362.45). Local rules (landlords, HOAs, city codes) can add more; this is a summary, not legal advice.

Growing, then drying, through a San Dimas year

Plan the drying space before harvest week. A garage or spare room open to October air starts out dry, so the outside of each bud can lose water faster than the inside. Dry in a closed, dark room, hang a hygrometer (a humidity gauge) by the drying line, and add a small humidifier when it reads low. Before the buds go into jars, a stem should bend a little before it snaps.

Before that comes the heat. The Pomona/Fairplex station, 2.9 miles away, averages a 92°F August afternoon and about 71 afternoons a year at 90°F or hotter, most of them from July through September. A garage tent wants its lamp running at night from June through September, when lows run 57 to 63°F. Air drawn in after dark is usually the cheapest cooling you have.

Dryness reaches the growing plants too. Humidity averaged 63 percent in June 2024 and fell to 50 by August, while afternoons warmed by about 8 degrees. Hot, dry air pulls water through leaves faster, so pots dry out sooner in August than in June. Seedlings and fresh clones feel it first; a humidity dome over their first week helps.

Winter turns the garage the other way. December averages a 42°F low, and the station counts about 3 freezing nights a year, most of them in December and January. Run the lamp through the coldest hours, before dawn, and put a seedling mat under young roots.

Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high °F	68	67	72	76	78	84	90	92	89	81	74	67
Avg low °F	43	45	47	50	54	57	62	63	60	54	47	42
Humidity %	64					63	53	50	55	44

Highs and lows: NOAA 1991 to 2020 normals, Pomona/Fairplex station (2.9 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.

Outdoors in San Dimas

Under California law, the limit is 6 living plants per private residence, however many adults live there. Each one needs a locked spot shielded from the view of anyone in a public place. A city or county can add reasonable rules for indoor grows and can forbid outdoor growing outright, so confirm which rules your address falls under first.

If outdoor growing is permitted at your address, start seeds indoors March 4 to March 18 and set plants out from April 15; autoflowers get sown about a week ahead of planting out. Nights average 50°F or warmer from April 18 to November 2. Mold pressure was low in the 2024 fall air, so heat and thirst are the outdoor risks to plan for. Mulch the pots, water early, and shade them on the hottest afternoons.

Frost	Rare: about 2.7 freezing nights a year
Nights stay 50°F or warmer	Apr 18 to Nov 2
Start seeds or clones indoors	Mar 4 to Mar 18
Move plants outdoors	Apr 15 or later

Your San Dimas grow, kept close

San Dimas has kept its old western downtown and a small-town feel, and in a small city a garage door that stays shut all summer can draw a question or two. The drying routine that finally worked is worth keeping to yourself.

Canna GLAP turns each grow record into ciphertext on your phone before the upload starts, and the key to read it opens only with your passphrase. Should someone reach our servers uninvited, they would find grow data that no one there can open. That protection covers the journal only; it does nothing about the smell of a drying room on a warm October evening.

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 Dimas ask

How do I keep cannabis from drying too fast in San Dimas?

Dry in a closed, dark room rather than an open garage, and add moisture if the hygrometer reads low. In 2024 the outside air was at its driest of the months shown in October, right in harvest season for outdoor plants.

Does San Dimas get frost?

Only on a few nights, mostly in December and January. The average night stays at 45°F or warmer from February 21 to November 26, so frost rarely touches a spring or summer run.

How hot does San Dimas get in summer?

August afternoons average about 92°F, with around 19 days that month at 90°F or more at the Fairplex station. Run the lights at night and read the tent's temperature at the canopy, not the floor.

Growing near San Dimas

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