The Nor'west arch is a weather pattern peculiar to the east coast of New Zealand's South Island. For this reason, it is also often referred to as the Canterbury arch, although it is visible in both Otago and Marlborough as well as in the Canterbury Region. It is shown in an apparent arch of high white cloud in an otherwise clear blue sky over the Southern Alps, and is accompanied by a strong hot northwesterly or northerly wind simply known as The Nor'wester.
Closer to the Canterbury coast, some distance from the mountains of the Southern Alps, it appears as a clear area of blue above the mountains, with white cloud streaming to the east from it. The phenomenon is similar to the Chinook arch seen in the Pacific regions of the United States and Canada.