It's hot, then cold, then hot again. Who's to know how we should be dressing in a world that no longer has any discernible climate? Designers, that's who. They know the importance of a trans-seasonal wardrobe more than most, and that's why they were showing their cruise collections in New York last week.

Cruise, or "resort" as it's known by some, is an interesting concept that bridges the gap between autumn and summer collections. Arriving in the shops in January, it's designed for warmer climes and the grande dames who holiday in them. After all, your average Joe has no need for a pair of hotpants in February.

But where cruise collections were once the esoteric preserve of tencel trousers and a tropical-print kaftan, nowadays they serve several more practical purposes. They're a commercial must for fashion houses whose main collection is beginning to look a little tired after three months of editorial coverage and another three on the shop floor, injecting a little pizzazz and hinting at what's to come in the summer. Fashion tyrant Anna Wintour loves a bit of cruise, because the micro-campaigns buff up her ad revenue during the leaner months after Christmas.

It'll also perk up your wardrobe: hybridisation is key, so look for pieces that will work in hot and cold. Marc Jacobs' stripe dress goes with bare legs, tights or over jeans, and Alexander Wang's goddess dress in sporty marl-grey jersey is glam but casual. Over at Prada, there were bold, smart shirts tucked into bikini bottoms – it's certainly one way of letting the office know you're about to hit the beach for a couple of weeks.