CannaGLAP
Grow cannabis in Windsor, CA
Growing cannabis in Windsor: the cold half of the year sets the plan
Windsor freezes more often than its warm summer afternoons suggest. A typical year brings about a month's worth of nights at 32°F or colder, and nearly 11 of them fall in December alone.
Those cold nights shape the indoor grow, and they hold the outdoor season back until May. If your tent sits in a garage, has it ever been tested against a December cold snap?
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.
Keeping a Windsor grow warm, and cool when needed
The cold settles in December and January. At the Santa Rosa airport station, 3 miles away at 114 feet, nights average about 37 and 38°F in those months, and January brings about 9 freezing nights. A tent in a garage or an insulated outbuilding loses its lamp heat fast after lights out. Schedule the lamp across the coldest hours, from around midnight into the morning, and lift pots off a cold slab floor.
Spring nights stay cold for a while. The average night does not reach 45°F until early May, and March lows sit near 41. Seeds and clones started in late March root slowly in a cool garage, so a little warmth under the tray and a clear lid to hold humidity pay off.
Summer asks for less. Average highs reach about 84°F in July and August, and September brings the most 90-degree afternoons, about 8. Nights in the low 50s flush heat out of a tent after lights off, so run the lamp at night only through a hot spell. An air conditioner dries the room only while it runs, and on nights this cool it seldom does.
In 2024 the outdoor air averaged 50 percent humidity in June, 58 in August and 64 in September, then fell to 53 in October. January averaged 83 percent, which matters mostly in an unheated garage; there, a dehumidifier helps through winter as well.
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 58 | 62 | 65 | 69 | 75 | 82 | 84 | 84 | 83 | 77 | 65 | 58 |
| Avg low °F | 38 | 39 | 41 | 43 | 47 | 50 | 52 | 52 | 50 | 46 | 40 | 37 |
| Humidity % | 83 | 50 | 54 | 58 | 64 | 53 |
Highs and lows: NOAA 1991 to 2020 normals, Santa Rosa Sonoma Co Airport station (3 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.
Windsor's outdoor window
California permits 6 living plants per private residence, no matter how many adults live in it, kept locked and out of sight from any public place. Local rules can extend to indoor grows and can ban outdoor plants, so confirm what applies at your home first. With outdoor plants allowed, start photoperiod seeds March 20 to April 3 and set plants out from May 1. Frost usually ends around March 2 and comes after April 2 only one spring in ten, but the cold nights, not frost, set the planting date.
From then, about 184 days remain before an early frost, the kind that arrives by November 1 roughly one fall in ten. Photoperiods ripen in October, when nights average about 46°F and growth slows. In 2024, September carried the dampest air of June to October, at 64 percent, so check the thickest colas (the main bud clusters) closely that month. Autoflowers, sown days before planting out, can finish in summer's drier air.
| Last spring frost | Mar 2 in a typical year, Apr 2 to be safe (later only 1 year in 10) |
|---|---|
| First fall frost | Nov 20 typical, as early as Nov 1 (1 year in 10) |
| Frost-free season | about 262 days |
| Nights stay 50°F or warmer | Jun 15 to Sep 10 |
| Start seeds or clones indoors | Mar 20 to Apr 3 |
| Move plants outdoors | May 1 or later |
A Windsor grow, kept off the record
Between the Sunday farmers market on the Town Green and the short drives to nearby Healdsburg and Santa Rosa, you will meet plenty of people who grow something. How much you say about your own plants is your call.
Canna GLAP seals each grow record on the phone before it uploads, so the record that reaches our servers is ciphertext. An intruder who got in would have unreadable grow files and no key. That protection covers the journal only; it cannot hide a flowering plant's smell from the house next door.
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 Windsor ask
When should I plant cannabis outside in Windsor?
At the start of May, if local rules allow, once the average night holds at 45°F. Start photoperiod seeds indoors in late March so they are ready by then.
Does Windsor freeze often enough to matter for an indoor grow?
For a garage or outbuilding grow, yes. Freezing nights cluster from November through February, so a tent there needs warmth at the roots once the lights go off.
Is September or October the riskier month for Windsor buds?
In 2024 September brought the damper air and October the colder nights, so outdoor buds face mold risk first, then slow, chilly ripening after it.
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