On Sunday, the mercury hit a high of 29.1 degrees at 3pm, with a stifling overnight low of 15.2.

But a cool change caused the temperature to drop nearly ten degrees to 20.5 degrees on Monday.

However the Bureau of Meteorology has predicted the mercury would drop even further on Wednesday.

A low pressure trough is moving northeastward will bring a cooler change to southern parts of NSW and northern Victoria.

On the Border temperatures are predicted to drop back into single figures, with minimum temperatures to reach seven degrees on Tuesday and two degrees on Wednesday.

IN OTHER NEWS:

Showers, but no substantial rain is expected across the region on Tuesday, and snow could fall to 1000m.

Bureau senior forecaster Keris Arndt said clear skies on Wednesday result in frost in some areas of Victoria.

"The weather generally jumps up and down a lot during spring," he said.

"It's not something we see every week in October but it's not unheard of."

The cool interlude follows a drier and warmer than average start to spring in Northern Victoria and Southern NSW.

Culcairn experienced the driest recorded September for at least 20 years, recording just 11.4mm, well below the town's average rainfall of 51.4mm.

Across the border, Rutherglen recorded its highest minimum temperature in more than a century.

On September 21 the temperature reached a balmy minimum of 18.7 degrees, making it the warmest minimum temperature in the 102 years since September 28 1928 when it reached 28.