A series of powerful solar flares have caused a global climate shift on Pandora, making daytime truly deadly due to volcanic temperatures, forcing both humanity and the Na’vi to switch to nighttime wakefulness. Human houses with working air conditioners are now the only islands of safety in the middle of the wastelands scorched by the merciless sun, and those without a permanent shelter are forced to wander at nights from one settlement to another in the hope that someone will let them in, helping to avoid the fate of being burned alive by the sun.

The sun is merciless during the day, and it is impossible to stand in the open air at such temperatures without getting burnt. It takes several minutes of exposure to the burning rays to cause second-degree burns on the skin, and within half an hour, the burns become third-degree and then fourth-degree.

At night, the situation is a little bit better. The temperatures do drop significantly enough, and that's when most people (Na'vi and humans) try to leave the relative comfort of their houses to do errands like collecting food, supplies and water.

The majority of the plants and animals, however, are nocturnal. Some of them have adapted to the scorching temperatures of day, being active only in the night for the most part.

The nights are also when hunting is more efficient. The animals are more visible against the dark, and it is also harder for them to notice the hunters' approach since their vision is based on the motion, and the nights are more quiet.

And the nights are the only period of time when the weather is most predictable. During the day, the temperatures can go up to a hundred degrees Celsius and more, but they can also drop to freezing temperatures in the course of a few minutes, the weather is changing so erratically that it's almost impossible to forecast it.