Temperature is important factor in plant health as it affects many essential processes such as photosynthesis, respiration, transpiration and growth. All plants have a maximum and a minimum temperature that they can survive in; the majority of species respond well in the mid-range of temperatures, about 10-21°C (50-70°F), whilst the maximum temperature that they can endure is generally around 35°C (96°F). The minimum temperature varies from species to species, and extremely low temperatures can physically destroy plant tissue.

Altitude levels affect the temperature; in general, the air temperature rises by 0.5°C (1°F) for every 300 m (1,000 ft) drop in altitude. The temperature of the air around plants in a particular site may be raised by providing shelter, allowing them to enjoy the full warming effect of the sun without any cooling breezes.

The soil temperature affects a plant's ability to absorb water and nutrients from the soil, and the right temperature is also vital for establishing good, healthy, root growth. Clay soils usually take longer to warm up in the spring than sandy soils, as do north-facing slopes. Plots that slant gently towards the south tend to warm up quickly and so are ideal for growing early vegetable crops.

A drop in soil and air temperature is the signal for many plants to enter dormancy: a state where woody plants shed their leaves and herbaceous and bulbous plants die back and remain below the ground for the winter. A knowledge of dormancy temperatures can be useful to the gardener; shrubs may be kept dormant in cold storage until the soil is warm enough for planting, whilst bulbs may be brought out of dormancy by placing in a warm greenhouse to produce early flowers.