CannaGLAP

Grow cannabis in San Carlos, CA

Growing cannabis in San Carlos: easy summers, and a winter garage that runs cold and wet

In San Carlos, the season that tests a garage grow is winter. Summer afternoons stay mild, and hot ones are few. Then December and January nights average near 40°F, and frost turns up a couple of times in each of those months.

A heated bedroom barely notices. A garage takes in the outside air, cold and wet together. So which room is your next winter run going into, and what will keep it comfortable there?

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.

A San Carlos grow through the cold months

Put the lamp's heat where the cold is. At the Redwood City station, 2.4 miles away, average nights fall below 45°F from about November 10 to March 22. Through that stretch, run the lights overnight so their warmth lands in the coldest hours, and let the dark period fall in the afternoon. A seedling mat keeps young roots from stalling.

Cold brings damp with it. January's outdoor air averaged 85 percent humidity in 2024. Inside a heated house that number fades, because warming air lowers its humidity. In an unheated garage it does not, and a tent there can sit cool and wet for weeks. A small dehumidifier on a humidistat (a switch that holds a set humidity) belongs in that garage all winter.

Summer asks far less. The station counts about 18 afternoons a year at 90°F or hotter, and September holds the most, about 4. On those days, overnight lights keep the tent's lit hours out of the heat. Humidity climbed from 63 percent in July 2024 to 70 in August and September, so the dehumidifier earns a second season in late summer flower before October eased to 57.

MonthJanFebMarAprMayJunJulAugSepOctNovDec
Avg high °F596265697379818179756559
Avg low °F414345475054575754504440
Humidity %856463707057

Highs and lows: NOAA 1991 to 2020 normals, Redwood City station (2.4 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.

Planting out in San Carlos

Under state law, a private residence may keep 6 living plants, no matter how many adults live in it, behind a lock and out of sight from any public place. Cities and counties can put reasonable rules on indoor grows, though they cannot ban them. They may forbid outdoor plants, so find the rules for your own address before you dig.

Where a yard grow is allowed, sow indoors March 4 to 18 and plant out from April 15. Autoflowers, which bloom on age rather than day length, go in about a week after sowing. Frost has come by November 24 only one fall in ten, about 223 days after planting. Nights set the real limit: they average under 50°F after October 14, which slows ripening. October's drier air helps a late finish, so pick varieties that ripen in its first half.

Last spring frostJan 17 in a typical year, Feb 16 to be safe (later only 1 year in 10)
First fall frostDec 12 typical, as early as Nov 24 (1 year in 10)
Frost-free seasonabout 333 days
Nights stay 50°F or warmerMay 12 to Oct 14
Start seeds or clones indoorsMar 4 to Mar 18
Move plants outdoorsApr 15 or later

Your San Carlos records, sealed

San Carlos is a small city where people cross paths often, over dinner on Laurel Street or out along El Camino. A neighbor who spots a garage light burning at 3 a.m. in January may wonder about it. The notes behind that light are yours to share or keep.

Each grow record is encrypted on your phone first, and only the coded copy goes up to our servers, while the key that opens it stays with you. Anyone who broke into those servers would carry off grow data they could not read. The lock covers the journal, not the hum of a dehumidifier through the garage 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 San Carlos ask

Does San Carlos get frost?

Yes, a little. The typical last spring frost comes around January 17, and one spring in ten a frost comes after February 16. Most of the freezing nights fall in December and January.

Do I need a dehumidifier for a garage grow in San Carlos?

In winter, yes, if the garage is unheated, since cold outdoor air stays damp in there. In late summer it helps again: August and September both averaged 70 percent humidity in 2024.

Should I run grow lights at night in San Carlos?

Through the cold months, yes: an overnight lamp heats the tent during the coldest hours. In summer the same schedule moves the few hot afternoons into the dark period.

Growing near San Carlos

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