Climate and weather

Weather

Weather is the result of atmospheric conditions over a short period of time. When we think of weather, we think of temperature, precipitation, humidity, cloudiness, wind and atmospheric pressure. Weather conditions can change in a manner of minutes – for example, a warm sunny day can be interspersed with sudden showers.

Climate

Climate is defined as the weather conditions of an area averaged over a series of years, usually 30 years or more. Climate is the weather conditions we expect at certain times of the year based on long-term observations from instrumental monitoring, generational observation and mātauranga Māori. For example, we expect late summer to early autumn to be the driest time of the year for much of Aotearoa.

Influences on weather

Often, westerly winds move weather systems eastwards over the country. Due to the country’s long, slender north-to-south orientation, most of the weather in Aotearoa comes from these westerly flows. However, weather systems can also bring air from tropical or polar regions along with heavy rainfalls or cold showery precipitation.

Influences on climate

The climate is influenced by several factors. The first is geographic location. The country is located across latitudes 34° to 47° south – about midway from the equator, which influences the concentration of sunlight we receive. The second factor is the sea. The relatively mild sea-surface temperatures moderate the temperatures on the land. The third factor is topography. The mountains and highlands act as barriers to westerly weather systems. This effect is most obvious in the South Island’s West Coast – the wettest region – while over the divide is inland Otago – one of the driest regions. Topography also affects temperatures – generally, the higher the altitude, the cooler the climate.
Humans also have an effect on climate. By adding greenhouse gases to the atmosphere, we are changing the delicate balance of energy entering and leaving the Earth’s atmosphere. This extra energy trapped in the atmosphere is leading to changes in local and global climates.