Grow cannabis in Ceres, CA

Growing cannabis in Ceres: a garage that runs too dry in July and too damp in January

Ceres, beside Modesto on Highway 99, has two very different kinds of air. Humidity averaged 31 percent in July 2024. In January it averaged 85.

A heated house hides most of that January damp. A garage, a shed or an unheated back room does not. If your tent lives out there, is it set up for the month you are actually in?

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.

One Ceres garage, two seasons of work

From December into February the garage is the hard place. The Modesto airport station, 2.1 miles away, averages lows near 39°F in December and January, with about 5 or 6 freezing nights in each. When the lamp switches off, the garage air cools toward that, and as it cools its relative humidity can climb quickly, beading water on cold tent walls. Run the lights through the night so the cold hours are the lit ones, and set a small dehumidifier to run in the dark period.

By July the job turns around. The station counts about 26 days at 90°F in July and 23 in August, with July highs near 95°F, though nights still cool to about 63°F. A lamp on the night shift meets the coolest air, and an air conditioner handles the afternoons. That cooling dries the space further while it runs, so seedlings and fresh cuttings need a dome or a humidifier for their first weeks.

September and October sit between the two. Both averaged 41 percent in 2024, with October highs near 79°F, so a flowering tent can usually finish without a dehumidifier in those months. Harvests dry easily then, sometimes too easily: hang them in a cool, closed room rather than a garage that warms through the afternoon.

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	56	62	68	74	82	90	95	94	89	79	66	56
Avg low °F	39	42	45	48	54	59	63	62	59	52	43	39
Humidity %	85					33	31	35	41	41

Highs and lows: NOAA 1991 to 2020 normals, Modesto City Co Airport station (2.1 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.

The Ceres outdoor calendar

A California home may keep 6 living plants, regardless of how many adults live there, grown in a locked space that cannot be seen from public places. Cities and counties can put reasonable rules on indoor grows too, and may ban outdoor plants, so check what Ceres allows before planting.

Where it is allowed, frost leaves early, typically by the end of January, and after February 25 only about one spring in ten. Plant out from April 15, when April nights average about 48°F, with photoperiod seeds started indoors March 4 to 18; autoflowers go in about a week before planting. From there a plant has about 219 days before an early first frost around November 20. Summer is the test: June through September bring roughly 80 afternoons at 90°F, so water deeply in the morning and shade plants through the hottest hours. In the dry fall air, ripe buds risk drying too fast after the cut more than they risk mold.

Last spring frost	Jan 31 in a typical year, Feb 25 to be safe (later only 1 year in 10)
First fall frost	Dec 5 typical, as early as Nov 20 (1 year in 10)
Frost-free season	about 312 days
Nights stay 50°F or warmer	Apr 25 to Oct 21
Start seeds or clones indoors	Mar 4 to Mar 18
Move plants outdoors	Apr 15 or later

A garage grow and a private record

A garage grow is the easiest kind to notice. A door left up on a warm evening, a neighbor in the next driveway, the steady hum of a fan: encryption cannot close the garage door for you or hide what drifts out of it.

It can keep your journal to yourself. Canna GLAP encrypts your grow records on the phone and uploads them in a form only your passphrase can open. Anyone who broke into our servers would get grow records with no way to open them. The winter dehumidifier timing you worked out stays your own.

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 Ceres ask

Does a Ceres garage grow need a heater in winter?

Usually a little help. December and January nights average near 39°F at the station, so lights that run through the night plus a seedling mat cover most of it.

Can outdoor cannabis stay out into November in Ceres?

Often. A typical first frost holds off until about December 5, though an early one comes around November 20. Average nights drop below 45°F after November 9, so growth slows first.

Do I need a dehumidifier in Ceres?

In summer, rarely, since the air ran dry from June through October in 2024. In winter, yes for a tent in a garage or other unheated space, where the damp January air reaches it.

Growing near Ceres

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