The rainforest biome remains warm all year and must stay frost-free. The average daily temperatures range from 20°C (68°F) to 25°C (77°F).

There are two types of rainforests, tropical and temperate. Tropical rainforests are found closer to the equator where it is warm. Temperate rainforests are found near the cooler coastal areas further north or south of the equator.

The tropical rainforest is a hot, moist biome where it rains all year long. It is known for its dense canopies of vegetation that form three different layers. The top layer or canopy contains giant trees that grow to heights of 75 m (about 250 ft) or more. This layer of vegetation prevents much of the sunlight from reaching the ground. Thick, woody vines are also found in the canopy. They climb trees in the canopy to reach for sunlight. The middle layer, or understory, is made up of vines, smaller trees, ferns, and palms. A large number of plants from this level are used as common houseplants. Because of the small amount of sunlight and rainfall these plants receive, they adapt easily to home environments. The bottom layer or floor of the rainforest is covered with wet leaves and leaf litter. This material decomposes rapidly in the wet, warm conditions (like a compost pile) sending nutrients back into the soil. Few plants are found on the floor of the forest due to the lack of sunlight. However, the hot, moist atmosphere and all the dead plant material create the perfect conditions in which bacteria and other microorganisms can thrive.

Tropical rainforest soils are primarily composed of ultisols and oxisols. Although these soils are rich in aluminum oxide and iron oxide–which gives the soil its red color–tropical rainforest soil fertility is actually quite low. Over two-thirds of the world's rainforests, and three-fourths of the Amazonian rainforest can be considered "wet deserts" in that they grow on red and yellow clay-like soils which are acidic and low in nutrients. Tropical rainforest soil is very thin and low in nutrients. With no winters or frosts to kill insects or microorganisms, and with lots of heat and humidity to help them grow and multiply, organic matter such as fallen leaves and twigs decomposes so quickly that only a thin layer of organic material covers the soils. The soils are heavily leached of nutrients by rainwater. But in many cases that doesn't matter much because the nutrients are absorbed by other life forms before the rain has a chance to carry them away. Trees absorb the nutrients with thick mats of rootlets that grow close to the surface of the soil. Rainforest soils are generally terrible for agriculture, producing crops for one to three years before being depleted of nutrients. How is it then that a tropical rainforest is so rich in life? The secret is a quick turnover of nutrients. When leaves, trees, and plants of animals die they fall to the forest floor where they are quickly recycled into mulch by insects and fungi. Bacteria then play a crucial part in converting the mulch and litter into nutrients consumed by plants. The air at ground level in a tropical rainforest, according to Harvard biologist and ant specialist Edmond Wilson is "humid and saturated with odors of healthy decay."▸Only two organisms can break down dead plants into usable nutrients: bacteria and fungi. In wet, humid, dark, and hot conditions in the rainforest fungi and bacteria can break down cellulose very quickly. Since there is little wind in the forests. leaves tend to fall straight down. Thus, many plants fed on nutrients they themselves deposited. Termites also play a major role converting cellulose to nutrients that can be consumed by other animals. The termites themselves are a favorite food of many animals.