Transpower has announced more than $5 million in improvements to Hawke's Bay's power supply.

Since September 2000, there have been five events which caused significant power cuts in Hawke's Bay and Gisborne.

Four of those happened during extreme weather events, including lightning and snow storms.

Transpower said the the improvements will prevent or minimise the impact of extreme weather events - which records show appear to be happening more often.

The work at Redclyffe, Whirinaki and Wairakei substations - and on the major transmission line into the Hawkes Bay region - will start in September.