Looming bad weather and a fear that electricity may be out for days is worrying Canterbury farmers in the wake of this morning's quake.

A release from Federated Farmers just issued said that electricity is now the major concern for domestic water and farm operations - now that it is clear there were only minimal reports of injury.

"While reports are still coming in, it seems North Canterbury between Dunsandel and the Waimakariri River has suffered the brunt of damage in the rural sector," said Neil Stott, Federated Farmers North Canterbury provincial president.

"Farmers were currently checking essential farm infrastructure, said Stott. His dairy chairperson, Kieran Stone, had received reports "of damage near Burnham involving a vat and reports of damage to a milking platform."

There had also been damage to grain silos in the Darfield area.

Of growing concern to farmers was a MetService weather warning that had been issued for Sunday evening - especially since power may not be restored to rural areas for up to two days.

WeatherWatch.co.nz said strong winds would increase during the day, with severe gales gusting to 130km/h possible later in the day.

MetService is also watching the storm, issuing a severe gale warning for the city predicting winds averaging 65km/h (gale force) with gusts to 130km/h.

"Winds of that speed can be damaging and with many buildings extensively damaged it could cause a major headache for emergency services," a spokesman said.

Canterbury electricity supplier Orion is confident that 90% of Christchurch city will have power restored by nightfall, says spokesman Roger Sutton.

He says rural areas will take longer, but the company is currently assessing how much damage has been done outside main centres.

He advises those whose houses have been damaged to turn power off at the mains.

Neil Stott said that a number of farmers had invested in backup generators but these were "a short-term fix".

"The welfare of livestock will now be of prime concern to farmers and we appreciate the offers now coming in from fellow farmers," said Stott.

"We would like to join officials in requesting that mobile phone use be restricted to essential calls. Farmers will be trying to arrange for generators and essential repairs.

A power outage at the Synlait dairy factory meant "jammed lines needed to be cleared" but the power was now back on there.

"Some Synlait suppliers have reported structural damage to milking platforms and are arranging alternate milking options with neighbouring farmers," said Stott

"Synlait is also diverting some supply, around four tankers, to New Zealand Dairies under an agreement it has with that company.

It was clear that a "number of skilled tradespeople" would be needed in rural areas over the next few weeks, said Stott.