CannaGLAP
Grow cannabis in Portland, OR
Growing cannabis in Portland: the damp arrives the same weeks your buds do
Portland growers rarely lose a plant to heat. July brings fewer than 4 days at 90°F, and a typical frost-free year runs about 280 days. What takes harvests in Multnomah County is water in the air: September averages 70 percent humidity and October 78, the exact weeks a photoperiod plant is packing on its densest flowers.
So ask yourself this: is your grow set up for the summer you have, or for the fall that actually decides your yield?
Adults 21 and over: yes. Plant limit: 4 per household, however many adults live there.
Four adults in one home still means 4 plants in total. Source: OLCC FAQ. Local rules (landlords, HOAs, city codes) can add more; this is a summary, not legal advice.
Inside a Portland grow: humidity first, everything else second
Most of the year, Portland air is wet. January averages 84 percent humidity, and lows hover near 37°F through December and January. A tent in a Southeast bungalow basement sits in that cool, damp air every time the lights go off, and that is when condensation forms on leaves and tent walls. In a basement like that, a small heater on a thermostat and a dehumidifier do more for a winter grow than a bigger light ever will; a tent in a heated upstairs room usually runs dry and can skip the dehumidifier until flower.
Flowering is where the dehumidifier earns its keep. Hold the tent well below the outdoor numbers in late flower, move air under the canopy as well as over it, and thin crowded inner branches so dense colas can dry between waterings. Check the biggest buds from the inside: bud rot starts near the stem and shows on the surface last.
Summer is the easy stretch. Highs average about 80°F in July and August, with only 3.8 and 4.1 days hitting 90°F, so a tent in a NE Alberta spare room rarely needs more than steady exhaust. July is also the driest of the months measured, at 55 percent, which makes midsummer the best window for an indoor flower cycle that finishes before the damp comes back.
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 | 47 | 51 | 56 | 61 | 68 | 73 | 80 | 81 | 75 | 63 | 52 | 46 |
| Avg low °F | 37 | 39 | 41 | 44 | 49 | 53 | 58 | 59 | 55 | 48 | 42 | 37 |
| Humidity % | 84 | 66 | 55 | 63 | 70 | 78 |
Highs and lows: NOAA 1991 to 2020 normals, Portland Kgw-Tv station (0.6 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.
Planting outdoors in Portland
Oregon sets its limit by household, not by person: four plants per home, however many adults live there, so four roommates still share four plants. Your lease or HOA may add rules of its own. Start seeds or clones indoors from March 9 to March 23 and move plants out on April 20 or later, when nights begin to average 45°F. Frost is rarely the problem; the first fall frost arrives by November 10 in only about one year in ten.
The damp is the problem. Nights average 50°F or warmer only until about October 7, and humidity keeps climbing from there. Choose strains bred to finish by late September, or plan to move plants under cover for their last weeks. Space them so wind can pass through, and stop watering late in the day once fall sets in.
| Last spring frost | Feb 25 in a typical year, Mar 21 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 280 days |
| Nights stay 50°F or warmer | May 20 to Oct 7 |
| Start seeds or clones indoors | Mar 9 to Mar 23 |
| Move plants outdoors | Apr 20 or later |
Your mold lessons are worth keeping private
Oregon counts four plants per household, so four roommates share one limit, and maybe one tent. Sharing the plants does not have to mean sharing every note. In most apps and spreadsheets those notes sit on a company's servers in readable form.
Canna GLAP encrypts the grow log on each phone before upload. If our servers were ever broken into, the thief would come away with encrypted grow records they have no key for. The mold lessons from a Southeast basement or a NE Alberta spare room stay with whoever earned them.
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 Portland ask
When do plants go outside in Portland?
April 20 or later, when average nights reach 45°F, after an indoor start for seeds or clones from March 9 to March 23. The last spring frost is typically around February 25, so cold nights, not frost, set the date.
What stops bud rot in a Portland fall?
Plan around September and October, which average 74 percent humidity together. Indoors, run a dehumidifier and move air under the canopy through late flower. Outdoors, pick plants that finish by late September or bring them under cover.
How many cannabis plants can I grow in Portland?
Four per household under Oregon law, no matter how many adults live in the home. Four adults sharing a house still means four plants in total.
Growing near Portland
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