Not all hard suitcases. The only exception is an intersection that is controlled by lights, where a green arrow indicates you can turn left. In the South Island particularly, it may take you longer than you imagine to get from one place to the next. Note that power outlets only accept flat three or two-pin plugs, depending on whether an earth connection is fitted. The warmest months are December, January and February, while the coldest are in June, July and August.
Winters tend to be short and generally fairly mild.
Summer and winter temperatures vary by only about 10'C over most of the country, making New Zealand an all year holiday destination. Clothing Dress is informal and relaxed on most occasions. Smart casual clothes are fine for almost anywhere. In summer a light jacket or sweater should be included in your luggage should the weather turn cooler or you visit the high country. You can expect some rain, so include a light waterproof jacket or coat.