"It is our greatest concern that we need to keep horses and people safe," he said.
Horses on-site for the event were to be put under cover. Horse trucks were asked to relocate away from trees all horses carry ID.
"If horses escape, we ask you not to panic," Mr Hansen said.
"Straight away all the gates will be radioed and they will be locked. The best thing for horses escaped in the dark is to stay calm and we will have people out there to try and catch that horse."
Competitors were advised to delay travelling to Hastings, with 100mm of rain and winds with 100km/h gusts likely to hit between 1am and 2pm today.
Those already on the road were asked to take their horses to the Hawke's Bay Racing Stables in Wall Rd after registration at the polo grounds.
A team of 25 would maintain vigil at the Showgrounds overnight to keep people and horses safe.
There are 8000sq m of marquees at the grounds, which were secured with extra strops and made off limits until high winds abated.
"I am very worried about the prognosis of the storm. However, I am confident we have robust systems in place that will ensure safety to all," Mr Hansen said. Today's competitions, showing and Welsh classes, were postponed but, from tomorrow onwards, "we are going to have a fantastic show here, for everyone to enjoy".
The forecast for the rest of the show week was "brilliant".
More than 2600 horse and rider combinations were expected to compete.
Civil Defence group manager Ian Macdonald said the situation was being closely monitored and preparations made for heavy swells and strong winds in coastal Hawke's Bay.
People were advised to be prepared for periods without electricity by readying torches, candles and an alternative cooking source.
"People need to make sure their family emergency plans are up to date, with their properties prepared for strong winds and a getaway kit all ready - just in case," he said.