A woman was cut by flying glass when an apparent tornado smashed through her car's rear window, sending stones and debris hurtling across a Kapiti Coast car park as witnesses scrambled for cover.

Mandy Butler was with her partner in the Paraparaumu car park when the tornado tore through about 1pm on Sunday, forcing them to duck for cover inside their car.

She said the tornado ripped through the area for about 10 seconds, pelting cars and people with debris.

She was cut on the arm by glass from her smashed rear window.

"[It] was so scary," she said.

The wind was so strong, said Butler, that she expected the damage to be worse.

Butler and her partner managed to cover the broken window with tarpaulins and duct tape before driving back to Wellington.

They made it home safely despite having to make the journey without a rear window, she said.

A local restaurateur who also witnessed the tornado said he saw seagulls being whipped around by the wind.

The car park was left strewn with debris and damaged vehicles.

Witnesses also praised staff at the local Mitre 10, who rushed out to help once the tornado passed.