Weather is not the same as climate. Weather is the condition of the air over a short time and it can change quickly. Climate is the average weather over a long period of time. Climate includes average temperature, humidity, sunshine, and the amount of rain and snow.

Temperature is a measure of heat. Only about one two-billionth of the sun's heat enters the atmosphere. The rest is lost in space. About 34 per cent of the sunlight that enters the atmosphere is reflected back into space. Clouds cause most of this reflection. Heat from the ground and oceans warms the atmosphere. The atmosphere absorbs the heat and prevents it from easily passing back into space. This causes what we call the greenhouse effect.

Air pressure is the force of air pressing on the earth. Temperature affects air pressure. Warm air is lighter than cool air. Warm air forms a low-pressure area, also called a low. Cool air forms a high-pressure area, or high. Air usually moves from high-pressure areas to low-pressure areas. High-pressure areas usually have clear skies. Low-pressure areas usually have cloudy skies.