# Temperature

> In growing, temperature usually means grow-room air temperature; cannabis grows best around 24–28 °C (75–82 °F) by day and a few degrees cooler at night.

- Canonical: https://genetixbay.com/knowledge/glossary/temperature.html
- Also written: air temperature, room temperature, day temperature, night temperature, grow room temperature, temps
- Glossary category: Environment and light · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Temperature sets the speed of nearly every process in a plant: [photosynthesis](https://genetixbay.com/knowledge/glossary/photosynthesis.md), respiration, water uptake and development. For cannabis, grow-room air temperature is the number most growers track, but [leaf temperature](https://genetixbay.com/knowledge/glossary/leaf-temperature.md) is what the plant actually experiences, and root-zone temperature matters separately.

## In practice

Common targets (air, under [LED](https://genetixbay.com/knowledge/glossary/led.md); [HPS](https://genetixbay.com/knowledge/glossary/hps.md) rooms run about 1–3 °C cooler for the same leaf temperature):

| Stage | Day | Night |
|---|---|---|
| Clones and [seedlings](https://genetixbay.com/knowledge/glossary/seedling.md) | 24–27 °C (75–81 °F) | 21–24 °C (70–75 °F) |
| Veg | 24–28 °C (75–82 °F) | 20–24 °C (68–75 °F) |
| Flower | 23–28 °C (73–82 °F) | 18–22 °C (64–72 °F) |
| Late flower | 20–26 °C (68–79 °F) | 17–21 °C (63–70 °F) |

Chandra and colleagues (2008) found cannabis leaf photosynthesis peaked around 25–30 °C at ambient [CO2](https://genetixbay.com/knowledge/glossary/co2-enrichment.md). Measure at canopy height in the shade of a leaf, not near the floor or the fixture. Keep roots in hydro around 18–22 °C (64–72 °F) for good dissolved oxygen.

## Don't confuse with

- **Leaf temperature**: often 1–3 °C below air under LED, and can be above air under HPS.
- **DIF**: the gap between day and night temperature.
- **Root-zone temperature**: medium or water temperature, a separate target.

## Related terms

[Leaf temperature](https://genetixbay.com/knowledge/glossary/leaf-temperature.md), [DIF](https://genetixbay.com/knowledge/glossary/dif.md), [Heat stress](https://genetixbay.com/knowledge/glossary/heat-stress.md), [VPD](https://genetixbay.com/knowledge/glossary/vpd.md), [Cold nights](https://genetixbay.com/knowledge/glossary/cold-nights.md)

## Read more

- [Temperature by stage: day, night and root-zone targets](https://genetixbay.com/knowledge/environment/temperature-by-stage.md)

## Sources

1. Chandra S, Lata H, Khan IA, ElSohly MA, 2008. Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions. Physiology and Molecular Biology of Plants 14(4):299–306. https://doi.org/10.1007/s12298-008-0027-x
2. Nelson JA, Bugbee B, 2015. Analysis of environmental effects on leaf temperature under sunlight, high pressure sodium and light emitting diodes. PLoS ONE 10(10): e0138930. https://pmc.ncbi.nlm.nih.gov/articles/PMC4598144/