Met Office forecasters predict thermometers could dip to zero overnight on Friday, January 17, and -3° in rural areas in the small hours of Sunday morning with frost making roads slippery.
The last time it got that cold in the county was way back on December 2.
January's mild weather has kept road surfaces well above freezing, apart from one precautionary early-morning run on January 10.
Highways England are responsible for gritting motorways and major roads including the A45 and A14, A5 and A43. But that still leaves 1,157 miles of A and B roads for the County Council's 22 gritting lorries to look after.
A Northamptonshire Highways spokesman said: "Our aim is to make roads as safe as is practical and ensure that you can travel with a minimum of delay and disruption during severe winter weather.
"Occasionally, gritting arrangements do not go to plan. You should never assume that a road has been treated but should drive in accordance with the prevailing conditions.
"Please remember that the majority of minor roads will receive no treatment at all."
According to Met Office figures, temperatures have stayed above 3° in Northamptonshire throughout January so far.
But, despite the chilly nights, long-range forecasters say there is no sign of snow before the end of the month and into early February.