A spell of warm weather across the South Island has come with warnings of strong winds and heavy rain, prompting advice for motorists to take extra care on the roads.

People travelling around the South Island over the weekend to make the most of higher temperatures were encouraged to plan ahead and factor in challenging driving conditions.

MetService said a range of weather warnings and watches were in place, with temperatures expected to climb above 30 degrees Celsius in some areas.

A strong wind warning covered parts of Canterbury, particularly the high country and areas near the foothills, from Saturday night through to Sunday.

Heavy rain warnings applied for Westland and Fiordland between Haast and Doubtful Sound from 3am Saturday, with further heavy rain expected from 11pm Saturday for the ranges of the Westland District about and north of Haast.

Wind and rain watches were also issued for much of the rest of the South Island, including Otago and Southland.

New Zealand Transport Agency urged road users to plan ahead and adjust their driving to suit the conditions on state highways.

The agency said heavy rain could lead to surface flooding, slips, and reduced traction, and motorists should consider lowering speeds, increasing following distances, avoiding sudden braking, and ensuring their vehicles remained visible.

Drivers of high sided vehicles, motorcycles, and vehicles towing trailers were advised to be especially cautious during periods of gale force winds.

State highways could face restrictions if obstructions occurred or where public safety was considered to be at risk.