Workers along the eastern flank of the country should be prepared for no ordinary day on the tools.

Temperatures in the 30s are due for a number of places today, with Christchurch likely to hit a January record of 36 degrees.

Occupational hygiene consultant Derek Miller told Kate Hawkesby Kiwis can be caught off guard due to the rarity of such conditions.

"It's important people have adequate water with them and start the day well-hydrated - but also have access to shade."

Miller says if possible people should rearrange their working hours.

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