The temperature of tropical rainforests varies little throughout the year.

The difference between the hottest and coldest months is much less than that between night and day.

High on tropical mountains hot days are followed by cold nights, often with frost.

The relatively high cloud cover and the high humidity tend to keep the daytime temperatures down. It is unusual for the temperature to reach 33 degrees centigrade (91°F).

The high humidity, however, does make the climate of the tropics feel hot, sticky and uncomfortable.

The subtropical zones, which experience seasonal rainfall, are much hotter than the equatorial zone, particularly just before the rainy season and at its start.

Isolated rainstorms clear the dust from the air on these first rainy days, which are interspersed with cloudless days when temperatures of 40 degrees centigrade (104°F) are common.

However, the humidity in the subtropics is usually lower, and so the level of discomfort is no greater than at the equator.

Most of the rain in the tropics falls as short, heavy showers. Sometimes low cloud and light rain will persist all day, but the more usual pattern is a warm, sunny morning with rapidly increasing cloud, culminating in a heavy afternoon shower that cools the air before evening.

During these storms, which do not last more than a few hours, an inch or two of rain is likely to fall.

However, if the rainfall continues, large daily totals result: 10 or even 20 inches (50cm) may fall within 24 hours, accompanied by thunder and lightning, and by strong squalls of wind that break branches and sometimes fell trees.

As a tropical storm approaches, large, threatening black clouds build up. The wind drops and everything is still. Even the birds become silent.

Flashes of lightning streak across the darkened sky, and occasionally the distant roar of the rain is heard between the claps of thunder, although normally these follow one another in a continuous roll.

A roaring cool wind arrives and is soon followed by the rain, which lashes down and drips through the forest canopy.

At the height of the storm, it is difficult to see more than a hundred yards ahead.

The rain often stops as suddenly as it began with perhaps a light drizzle continuing for a while.

Wisps of mist drift from the canopy and the jungle birds gradually start to call again.

Few places in the tropics are continually wet. Even in the wettest areas, there are predictable breaks in the rains, when fewer storms occur, or even dry spells lasting two to three weeks.

During these times, the forest plants must survive on the water stored in the soil from earlier rains. They use their few deep roots to draw on these reserves when the root-filled surface layers of the soil become dry. Such short, dry spells play an important role in triggering forest plants to flower and fruit of forest plants

The amount of wind in the tropical rainforest decreases enormously from the canopy to the ground.

For every meter of air movement at two meters above the ground, there are 30 meters in the lower canopy, and 120 meters above the canopy (40 meters above the ground).

The understory is therefore a still environment, where delicate flowers and large insects can exist without being battered by strong winds.

The temperature range is greatest above the canopy and least in the understory

In the understory, leaves and branches prevent the sun's energy from reaching the ground. They also trap heat in the lower layers of the forest during the night.

The humidity of the air remains high day and night in the understory. It rarely falls below 95 per cent.

Above the canopy, the level of humidity fluctuates much more widely, both from day to night and from one day to the next.