# DIF

> DIF is day temperature minus night temperature; a larger positive DIF lengthens stems, while zero or negative DIF tends to keep plants shorter.

- Canonical: https://genetixbay.com/knowledge/glossary/dif.html
- Also written: day-night temperature difference, temperature differential, positive DIF, negative DIF, temperature DIF, day/night differential
- Glossary category: Environment and light · Evidence: Supported
- 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"

DIF (from "difference") is the day temperature minus the night temperature. A day of 26 °C and a night of 20 °C is a DIF of +6 °C (about +11 °F). Research on greenhouse ornamentals showed that stem elongation responds to DIF more than to average temperature: positive DIF increases [internode length](https://genetixbay.com/knowledge/glossary/internode.md), zero DIF reduces it, and negative DIF (cooler days than nights) reduces it further. A short temperature drop at dawn gives part of the effect.

## In practice

Growers use DIF mainly to manage [stretch](https://genetixbay.com/knowledge/glossary/stretch.md) in early flower. Keeping the gap small, around 0–4 °C (0–7 °F), may help restrain height in stretchy cultivars; a larger gap of 6–10 °C (11–18 °F) late in flower is often used for colour. Evidence in cannabis specifically is thin; the effect is well documented in other crops. *Supported* by extrapolation.

Watch the humidity side. When lights go off and the room cools quickly, [RH](https://genetixbay.com/knowledge/glossary/relative-humidity.md) climbs and may approach the [dew point](https://genetixbay.com/knowledge/glossary/dew-point.md) on leaves and buds, inviting [botrytis](https://genetixbay.com/knowledge/glossary/botrytis.md). Ramp temperature down, run [dehumidification](https://genetixbay.com/knowledge/glossary/dehumidifier.md) at lights-off, and keep air moving.

## Units and formula

DIF = day temperature − night temperature (°C or °F).

## Don't confuse with

- **Cold nights**: a large positive DIF used for colour; see that entry for what it does and does not do.
- **VPD**: humidity-driven, though DIF changes [VPD](https://genetixbay.com/knowledge/glossary/vpd.md) at night.

## Related terms

[Temperature](https://genetixbay.com/knowledge/glossary/temperature.md), [Stretch](https://genetixbay.com/knowledge/glossary/stretch.md), [Cold nights](https://genetixbay.com/knowledge/glossary/cold-nights.md), [Dew point](https://genetixbay.com/knowledge/glossary/dew-point.md)

## Read more

- [Temperature by stage: day, night and root-zone targets](https://genetixbay.com/knowledge/environment/temperature-by-stage.md)
- [Stretchy, leggy cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/stretching.md)