New Zealand's seasons are opposite those in the Northern Hemisphere: July-September is the coldest period, and December-March is the warmest. Overall, the climate is fairly mild with few extremes of temperatures. The average temperature ranges from 60 F/15 C in the upper regions of the North Island to 50 F/10 C near the bottom of the South Island. The west coast is generally wet, while the east coast suffers regular droughts.
The best months to visit are February and March, when summer is in full swing but New Zealand school holidays are over. Spring—mid-October through November—can be damp but very beautiful, with flowers and trees in bloom. During New Zealand's winter, expect rain, with snow at higher altitudes. Take a sweater and an umbrella no matter what time of year you visit. Bear in mind that this is a long, narrow country in the middle of the Southern Ocean, with nothing to shelter it from regular storms.