The weather affects the potential for contaminant loss both directly and indirectly. Rainfall dislodges soil particles and runoff transports them overland. The annual pattern of rainfall and temperatures also affects how much vegetation grows, and how quickly, utilising stored nutrients from the soil.

Most areas of New Zealand have between 600 and 1600 mm of rainfall, spread throughout the year with a dry period during the summer. Over the northern and central areas of New Zealand more rainfall falls in winter than in summer, whereas for much of the southern part of New Zealand, winter is the season of least rainfall. Mean annual temperatures range from 10°C in the south to 16°C in the north of New Zealand. The coldest month is usually July and the warmest month is usually January or February.


Checking the weather forecast before making decisions on day-to-day farming practices such as when to move stock, when to cultivate, irrigate, spray, fertilize, or when to protect against potentially damaging weather like heavy rainfall, snow, frost or high winds is considered good management practice.

It is essential to do specific high-risk activities when a period of fine weather is forecast. Pay attention to weekly and longer-range forecasts when scheduling works and preparing sites.

A full rainbow over a farm illumnated by sunlight amongst a rain storm