Water is constantly moving between the oceans, the atmosphere and the land. The Sun heats water in oceans, lakes and soil, and it evaporates to form water vapour. Plants also release water vapour from their leaves (transpiration).

As moist air rises it cools, and the water vapour condenses onto tiny dust particles to form clouds. When droplets join and become heavy enough they fall as precipitation. On land, water flows over the surface as runoff or soaks in by infiltration, eventually returning to the sea.

Air pressure is the push of the air above us. In a high-pressure system, air sinks; in a low-pressure system, air rises. Rising air cools, and cooler air cannot hold as much water vapour, so clouds form. Wind is air moving from high to low pressure.

Weather is the condition of the atmosphere at a particular place and time. Climate is the average pattern of weather in a region over a long period, usually at least 30 years.

Mean monthly data for a town over six months — Month 1: 28 °C, 110 mm · Month 2: 27 °C, 95 mm · Month 3: 24 °C, 80 mm · Month 4: 20 °C, 45 mm · Month 5: 16 °C, 30 mm · Month 6: 13 °C, 20 mm