‘Perfect set-up’ for hoar frost across region

As promised, Central Otago woke to picture postcard-like hoar frost conditions yesterday.

MetService first indicated on Tuesday that conditions were ripe for the frost to occur and, sure enough, it was delivered.

MetService meteorologist Tui McInnes said conditions had aligned to produce hoar frost across the region.

A car passes over Clyde’s red bridge in Central Otago in hoar frost conditions yesterday morning. PHOTOS: SHANNON THOMSON

"Overnight last night was basically the perfect set-up."

Hoar frosts occurred when air temperatures were below freezing and that, combined with any moisture in the air, led to that moisture freezing on to any surface it came into contact with, he said.

An overnight low from Tuesday going into yesterday morning of -7.7degC was recorded at the weather station at Alexandra Airport.

Mist hangs over the Clutha River looking towards the Clyde Dam in hoar frost conditions in Clyde.

The elevation of the site meant the ground temperature in Alexandra itself and surrounding areas such as Clyde was likely to be lower, Mr McInnes said.

The Alexandra and Clyde areas appeared to be the epicentre for cold conditions based on MetService recording stations with the station between Omakau and Alexandra recording a low of -5.8degC overnight while into the Teviot Valley conditions were relatively warmer with 0.2degC recorded in Roxburgh and -2.5degC in Millers Flat.

Oturehua recorded -10.1degC, in Patearoa the mercury fell to -8.4degC, and -8.1degC was recorded in Ranfurly.