CannaGLAP
Grow cannabis in Santa Rosa, CA
Growing cannabis in Santa Rosa: the warmest month is the one your buds ripen in
Santa Rosa saves its heat for last. The station, 1.1 miles away and 166 feet up, averages 84°F on September afternoons, warmer than July, and logs about 7 days that month at 90°F or hotter. The same September nights fall to about 51. That is a 33-degree gap on an average day, in the weeks a photoperiod plant is filling out its flowers.
So what happens inside your canopy when the air cools 33 degrees overnight?
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.
A Sonoma County tent: steady air, not more air
Mild weather keeps an indoor grow cheap to run here; the cool nights are the part to manage. From June through September, lows average about 51°F to 53°F while highs run 80°F to 84°F. A tent in a spare room or garage near Railroad Square or Montgomery Village holds steady if the lamps run through the night and early morning, when the outside air is coldest, and rest through the warm afternoon.
Moisture climbs as the season goes on. Humidity averaged 52 percent in June, 56 in July, 60 in August and 65 in September, the dampest of the months measured from June to October, before dropping to 53 in October. Cool air holds less water, so air that averages 65 percent over the day runs damper still as it chills toward dawn. In late flower, keep an exhaust fan pulling air out of the tent, a clip fan inside it, and a small dehumidifier ready for September.
Winter is cool, not harsh. December and January lows average about 38°F and the station counts about 15 freezing nights a year, most of them from December through February. A tent in an unheated garage needs warmth under the roots and lamps that run through the small hours, and January's 83 percent outdoor reading matters only if that space is damp as well as cold.
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 60 | 64 | 67 | 71 | 75 | 80 | 82 | 83 | 84 | 79 | 67 | 59 |
| Avg low °F | 38 | 40 | 42 | 44 | 48 | 51 | 52 | 53 | 51 | 48 | 42 | 38 |
| Humidity % | 83 | 52 | 56 | 60 | 65 | 53 |
Highs and lows: NOAA 1991 to 2020 normals, Santa Rosa station (1.1 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.
Outdoors in Santa Rosa: a long season, a damp finish
California allows 6 living plants per private residence, however many adults live there, in a locked space that is not visible from a public place. Cities and counties can regulate home grows and may ban outdoor ones, so check your local rules before you plant outside. If an outdoor spot is allowed and meets those conditions, start seeds March 13 to 27 and set plants out April 24, when nights first average 45°F. Frost usually ends around February 25 and is safely past by March 29.
The season is long: about 200 days from April 24 to an early first frost on November 10, enough for many photoperiod strains to finish. Nights of 50°F or warmer end around September 24 and September's air is the dampest of the June to October months measured, so give plants wide spacing, thin the inner leaves and check the densest buds for gray mold through late September and October.
| Last spring frost | Feb 25 in a typical year, Mar 29 to be safe (later only 1 year in 10) |
|---|---|
| First fall frost | Dec 1 typical, as early as Nov 10 (1 year in 10) |
| Frost-free season | about 279 days |
| Nights stay 50°F or warmer | Jun 5 to Sep 24 |
| Start seeds or clones indoors | Mar 13 to Mar 27 |
| Move plants outdoors | Apr 24 or later |
Wine country is a talkative place
Santa Rosa is a city of about 178,000 that keeps running into itself: at the Wednesday Night Market, around Old Courthouse Square, at the Sonoma County Harvest Fair. Some of the people in those crowds grow too, and harvest comparisons follow. How your own run went does not have to be part of them.
Your grow records are encrypted on your own phone before Canna GLAP uploads them. If our servers were broken into, the intruder would get only unreadable grow entries, with no key to make sense of them. You choose who sees the details.
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 Santa Rosa ask
When should I plant cannabis outside in Santa Rosa?
Set plants out April 24, when nights first average 45°F, from seeds started March 13 to 27. Check first that local rules allow an outdoor grow at your address.
Is bud rot a risk in Santa Rosa?
Yes, late in the season. Humidity rises from 52 percent in June to 65 in September, and nights near 51°F push it higher after dark. That lands right in late flower, so airflow matters most then.
How many cannabis plants can I grow in Santa Rosa?
California allows 6 living plants per private residence, no matter how many adults live there, in a locked space not visible from a public place.
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