# How much sun does outdoor cannabis need?

> Outdoor cannabis needs at least 6–8 hours of direct sun a day, and more is better: full summer sun reaches 1,500–2,000 µmol/m²/s at midday and a daily light integral of roughly 40–60 mol/m²/day on clear days. Yield rises roughly in proportion to light, so a part-shaded spot yields less, not nothing. Under about 4 hours of direct sun, expect thin, airy buds.

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- Topic: Outdoor growing · Type: Numbers
- Evidence: Supported · Status: Draft: awaiting expert review
- Full article: [PPFD and DLI by stage, with the evidence](https://genetixbay.com/knowledge/environment/ppfd-dli-by-stage.md)
- Also asked as: How many hours of direct sun does cannabis need? | Can cannabis grow in partial shade? | Sunlight needs for outdoor plants | Is 4 hours of sun enough? | Morning sun or afternoon sun for cannabis?
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Short answer

Give outdoor cannabis at least 6–8 hours of direct sun a day, and as much more as the site allows. Clear summer days deliver roughly 40–60 [mol/m²/day](https://genetixbay.com/knowledge/glossary/dli.md) of light, above most indoor flower rooms, and yield rises with every extra hour of direct sun. *Supported* for the light–yield link; the hour count is *Grower practice*.

## Why

More light, more grams. In two controlled trials, flower yield rose in proportion to canopy light from 120 to 1,800 [µmol/m²/s](https://genetixbay.com/knowledge/glossary/ppfd.md), with no change in potency per gram [1][2].

Outdoor light is generous but variable. Daily light integral changes with month, latitude and cloud; monthly maps show midsummer values far above winter ones across the United States [3].

Shade costs twice. Shaded plants make less and airier flower, and leaves and buds stay wet longer after dew or rain, which favours mildew and rot [4].

Light, not heat, is the goal. Midday summer sun reaches about 1,500–2,000 µmol/m²/s; the risk in hot climates is root and leaf heat, not the light itself.

## The numbers

| Direct sun per day | What to expect |
|---|---|
| 8 h or more | Full-size plants, dense buds |
| 6–8 h | Good results, somewhat smaller |
| 4–6 h | Smaller plants, airier buds |
| Under 4 h | Thin, airy buds; consider another site |

| Measure | Typical value |
|---|---|
| Midday summer sun | ~1,500–2,000 µmol/m²/s |
| Clear midsummer DLI | ~40–60 mol/m²/day |
| Indoor flower target (for comparison) | 35–56 mol/m²/day at 800–1,200 µmol/m²/s |

## What to do

1. Watch your site through a full sunny day in early summer and count direct-sun hours.
2. Prefer sites open to the south and east (north and east in the Southern Hemisphere).
3. Use containers if you need to move plants to follow the sun.
4. Prune overhanging branches before planting.
5. Harden indoor-raised plants off over 7–14 days.
6. In very hot climates, give roots shade and mulch, not the leaves.

## Common mistakes

- Judging a site in spring, before trees leaf out.
- Planting in a damp, shaded corner where buds never dry.
- Moving plants from a tent straight into midday sun.

## Related

- Full article: [PPFD and DLI by stage, with the evidence](https://genetixbay.com/knowledge/environment/ppfd-dli-by-stage.md)
- Answers: [Bigger, denser buds](https://genetixbay.com/knowledge/answers/how-to-get-bigger-denser-buds.md) · [Why buds are airy](https://genetixbay.com/knowledge/answers/why-are-my-buds-airy.md) · [Start indoors, move outside](https://genetixbay.com/knowledge/answers/start-indoors-move-outside.md)
- Terms: [DLI](https://genetixbay.com/knowledge/glossary/dli.md) · [outdoor growing](https://genetixbay.com/knowledge/glossary/outdoor-growing.md)

## Follow-up questions

**Can cannabis grow in partial shade?** Cannabis grows in partial shade but yields less, because flower yield rose roughly in proportion to light across 120–1,800 µmol/m²/s in controlled trials. A spot with 4–6 hours of direct sun gives smaller, airier buds than one with 8 or more. Shade also slows drying of dew and rain on buds, which raises bud-rot risk. Prune overhanging branches where you can.

**Is morning or afternoon sun better for cannabis?** Morning sun is usually more useful for outdoor cannabis than late-afternoon sun. Early light dries dew from leaves and buds sooner, cutting the hours of wetness that powdery mildew and bud rot need, while hot afternoon sun in warm climates adds heat stress. Given the choice, pick a site open to the east and south (north in the Southern Hemisphere). This is grower practice.

**Can outdoor cannabis get too much sun?** Outdoor cannabis rarely gets too much sun once hardened off, since yield kept rising up to 1,800 µmol/m²/s at canopy level in trials and midday summer sun reaches about 1,500–2,000. Trouble comes from heat and dryness rather than light: in very hot climates, afternoon shade, mulch and light-coloured containers protect roots. Indoor-raised plants need 7–14 days of hardening off to avoid bleaching.

## Sources

1. Rodriguez-Morrison V, Llewellyn D, Zheng Y, 2021. Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science 12:646020. https://doi.org/10.3389/fpls.2021.646020
2. Llewellyn D, Golem S, Foley E, Dinka S, Jones AMP, Zheng Y, 2022. Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content. Frontiers in Plant Science 13:974018. https://doi.org/10.3389/fpls.2022.974018
3. Faust JE, Logan J, 2018. Daily light integral: a research review and high-resolution maps of the United States. HortScience 53(9):1250-1257. https://doi.org/10.21273/HORTSCI13144-18
4. PNW Plant Disease Management Handbook. Hemp (Cannabis sativa) - Powdery Mildew. https://pnwhandbooks.org/plantdisease/host-disease/hemp-cannabis-sativa-powdery-mildew