Outdoor Cannabis Planting Dates by Zip Code
Enter your zip code to get outdoor planting windows for your location — including which strain types will have enough season to finish before your first frost.
These recommendations are for outdoor growing only. If you're growing indoors or in a greenhouse with supplemental lighting, you can grow any variety regardless of your location or time of year.
- Start your plants indoors roughly 2 to 3 weeks before you plan to move them outdoors.
- If you dont want to deal with massive plants, consider planting a little later in the season.
- If you move your plants outdoors in the peak of summer when it is really hot, make sure to have automatic watering in place for at least the first few weeks while the plants are getting established.
| Zone | Avg. Extreme Min. Temp. | Avg. First Frost | Avg. Last Frost |
|---|---|---|---|
| 1 | Below −60°F | Aug. 1 – Aug. 31 | May 31 – Jun. 1 |
| 2 | −60°F to −50°F | Aug. 1 – Aug. 31 | May 31 – Jun. 1 |
| 3 | −50°F to −40°F | Sept. 1 – Sept. 30 | May 1 – May 31 |
| 4 | −40°F to −30°F | Sept. 1 – Sept. 30 | May 1 – May 31 |
| 5 | −30°F to −20°F | Sept. 30 – Oct. 30 | March 30 – April 30 |
| 6 | −20°F to −10°F | Sept. 30 – Oct. 30 | March 30 – April 30 |
| 7 | −10°F to 0°F | Sept. 30 – Oct. 30 | March 30 – April 30 |
| 8 | 0°F to 10°F | Oct. 30 – Nov. 30 | Feb. 22 – March 30 |
| 9 | 10°F to 20°F | Nov. 30 – Dec. 30 | Jan. 30 – Feb. 28 |
| 10 | 20°F to 30°F | No usual frost | No usual frost |
| 11 | 30°F to 40°F | No usual frost | No usual frost |
| 12 | 40°F to 50°F | No usual frost | No usual frost |
| 13 | 50°F to 60°F | No usual frost | No usual frost |
How Daylight Hours Control Your Outdoor Cannabis Season
Most cannabis grows on a photoperiod. That means the plant uses day length as its signal to switch from building structure to producing flowers. During the long days of summer, a photoperiod plant stays in vegetative growth, putting on size and branching. Once daylight drops below a threshold (roughly 13 to 14 hours depending on the variety), the plant reads that as the approach of fall and starts flowering.
This is why your USDA hardiness zone matters so much for outdoor cannabis planning. It's not just about frost. It's about how much season you have between your last spring frost and the point in fall when days are short enough to start the flower clock. In northern zones, that window is tight. In southern zones, you have room for multiple runs, longer-flowering varieties, and a more relaxed schedule.
Autoflowering strains work differently. They don't respond to light at all. They flower based on age, finishing in around 10 weeks regardless of how many hours of sun they get. That makes them the safest choice for any grower dealing with a short or unpredictable season.
Outdoor Cannabis Planting Guide by USDA Zone
The zones below cover the range where most US home growers live. Enter your zip code in the tool above for dates specific to your exact location. These are general windows based on typical conditions in each zone.
Outdoor season: Late May through early September. Frost can return by late August in Zone 3. Full season photoperiods are a real gamble outdoors, but fast-finishing short season varieties can work if started indoors 3–4 weeks before transplant.
Best outdoor approach: Autoflowers started after last frost in late May, targeting a late August harvest. Short season photoperiods started indoors in early May and transplanted out after frost can finish before fall closes in.
Outdoor season: After last frost (late April to mid-May) through first frost (mid to late October). Short season photoperiods that trigger flowering in August can finish by October. Full season varieties are tight, so choose fast-finishing genetics.
Best outdoor approach: Short season photoperiods and autoflowers. Start autoflowers after frost for a September harvest, then stagger a second run.
Outdoor season: Mid-April through late October. A solid season for most photoperiod varieties. Plants put outside after last frost in late April have time to build solid vegetative structure before the August flowering trigger, with harvest arriving in October before hard frost.
Best outdoor approach: All three work here. Full season photoperiods, short season photoperiods, and autoflowers all have viable windows. Autoflowers can run two rounds.
Outdoor season: Early April through mid-November. One of the most forgiving zones for outdoor cannabis. Plants have plenty of vegetative time in spring, a natural flower trigger in late summer, and warm fall weather that lets plants finish without rushing. Mold management in humid fall conditions is the main thing to plan for.
Best outdoor approach: All three variety types work well. Two autoflower runs are comfortable. Full season photoperiods have time to develop fully before the October flowering trigger.
Outdoor season: March through November. Long growing season with mild winters. Full season photoperiods have all the time they need, and autoflowers can run two to three rounds from spring through fall. Heat management and mold resistance become more important than frost timing.
Best outdoor approach: Everything works. Aim for heat-tolerant genetics with open bud structure for the humid Southeast. Pacific Northwest Zone 8 growers should prioritize mold-resistant varieties for the wet fall.
Outdoor season: Nearly year-round in Zone 9, fully year-round in Zone 10. The outdoor growing challenge here isn't frost. It's the summer heat and the fact that day length stays high enough for a long time that photoperiod plants stay in vegetative growth well into fall. Harvest typically runs November through December for full season plants.
Best outdoor approach: Autoflowers any time. For photoperiods, start in early spring to get the full benefit of increasing then decreasing day length across the whole season.
How to Read Your Planting Window Results
When you enter your zip code above, the tool calculates three separate planting windows based on the actual solar data for your latitude and your estimated frost dates.
Plant Start and Plant By dates
The Plant Start date is the earliest you should put plants outside: the later of your last frost date or the date when day length is long enough to keep photoperiod plants in vegetative growth. Putting photoperiod plants out before day length supports vegetative growth can cause premature flowering (called "re-vegging"), which wastes weeks of the season.
The Plant By date is the latest you should transplant outdoors while still giving the plant enough vegetative time before the flowering trigger kicks in. Plants put out after this date won't have had enough time to build the structure that supports a good harvest.
The flowering trigger date
This is calculated from real solar math for your latitude: the specific date in late summer when daylight at your location drops below the threshold that triggers flowering in that variety type. For full season photoperiods, the trigger is around 13 hours. For short season varieties, it's closer to 14 hours, which is why they start flowering earlier in the summer and finish sooner.
Estimated harvest date
Harvest is estimated at 9 weeks after the flowering trigger. Most photoperiod cannabis varieties take 8–10 weeks to flower, so 9 weeks is a practical midpoint. Your specific variety may finish a week earlier or later, so check the strain's listed flowering time and adjust from there.
Frequently Asked Questions
-
What USDA zone is best for growing cannabis outdoors?Zones 6 through 9 give outdoor cannabis growers the most flexibility. Zone 7 is often considered the sweet spot: the season is long enough for full season photoperiods to finish comfortably, the fall is warm enough to avoid early frost problems, and all three variety types (autoflowers, full season, and short season) have viable outdoor windows. Zones 5 and below work well for autoflowers and short season varieties but may cut full season plants short.
-
When should I plant cannabis outdoors?After your last frost date and once nighttime temperatures are reliably above 50°F. For most of the US, that means late April to mid-May. Use the zip code tool above to get specific dates for your location. The tool also considers day length, which matters for photoperiod varieties. Planting too early when days are still short can cause photoperiod plants to flower prematurely before they've built any size.
-
What's the difference between full season and short season cannabis?Both are photoperiod varieties that flower based on day length, not age. The difference is the day length threshold that triggers flowering. Full season strains wait until days drop to roughly 13 hours before flowering, which happens in late summer or early fall. Short season strains begin flowering when days are still closer to 14 hours, earlier in the summer, which means they finish earlier and work better in northern zones or for growers who want an earlier harvest.
-
Can autoflowers be grown in any USDA zone?Autoflowers can be grown in any zone that has at least 10 consecutive frost-free weeks. Because they don't respond to day length, they're not constrained by the photoperiod growing season. They just need warm temperatures and enough time to complete their cycle. In Zones 3 and 4, the frost-free window can be tight (sometimes under 90 days), but a well-timed run started right after last frost will usually finish before fall frost arrives.
-
What happens if my plants are still outside when frost hits?Young seedlings and plants in early vegetative growth are very frost-sensitive and can be killed by temperatures near 32°F. Mature plants in late flower are more tolerant. A light frost in the 28–32°F range for a few hours typically won't ruin a harvest, though it will add stress and slow resin production. Hard, sustained freezes will damage buds. If frost is forecast and your plants aren't ready, covering them overnight with fabric row covers buys a few more days without significant harm.
-
How do I find my USDA hardiness zone by zip code?Enter your zip code in the tool at the top of this page. It returns your USDA zone, estimated frost dates, and outdoor planting windows for each cannabis variety type, all based on the actual daylight hours for your location. You can also look up your zone directly on the USDA Plant Hardiness Zone Map.
-
Are cannabis seeds legal to buy in my state?All seeds sold by Triangle Hemp are legal to purchase and ship anywhere in the US. What varies by state is whether you can legally germinate and grow them. Home cultivation laws differ significantly across the country, from states with no restrictions to states where growing at home is still prohibited. See our state home grow guides for a breakdown of what's legal where you live, including plant limits, security requirements, and possession rules.
