Westland National Park (Fox Glacier) in May

March through May gives you the best balance of decent weather and fewer crowds. September to November works too — spring brings longer days and active wildlife. Summer (December-February) means peak crowds and higher accommodation prices, but also the most stable weather for helicopter flights. Winter hiking is possible but expect shorter days and more rain. Here's the insider tip: check the weather forecast and be flexible. Clear days are gold on the West Coast. If you wake up to blue skies, cancel your other plans and head to the glacier. Cloudy days are perfect for the rainforest walks around Lake Matheson or the coastal tracks near Gillespies Beach.