The temperature at Altnaharra was recorded on Tuesday morning and is the coldest temperature recorded there since 2010, Met Office spokesperson Nicola Maxey said.
She said temperatures could plunge further on Wednesday night into Thursday, but that conditions across the UK are set to get milder towards the weekend.
The spell of cold winter weather is showing no sign of slowing down as snow and ice warnings remain in place for parts of Scotland for this week.
An amber warning for snow is currently in place in central Scotland where the countries main cities including Edinburgh and Glasgow have seen travel disruption due to the rare heavy snow fall.
Other places further north, including Braemar, have seen up to about 70cm of snow.