Summer's latest dose of bad weather has brought snow to the South Island.

Snow was falling and settling on Porters Pass this afternoon, and hail was falling at Arthur's Pass, WeatherWatch.co.nz said.

MetService this morning issued a severe thunderstorm watch, which said there was a moderate risk of storms from north Canterbury to Wairarapa this afternoon.

It would bring localised rain and hail, especially in Marlborough where a few of the thunderstorms could be severe and could bring large hail of at least 20 millimetres in diameter.

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There was also a low risk of isolated thunderstorms from northern Canterbury and Westland up to southern Taranaki, Wanganui and Hawke's Bay this afternoon and evening.

The lower South Island would also be hit by the bad weather, where isolated thunderstorms, rain and hail were possible, MetService said.

However, come Tuesday the wintry conditions should move away and let summer return, WeatherWatch said.