The very light snow flurries came on a day when temperatures struggled to get above 0C.
And they will plummet to around -6C tonight, with Gardai warning of ice on some roads which have wet surfaces overnight.
But while the rest of the county continues with sub-zero temperatures on Sunday, Donegal will be warmer.
“There could be pockets of somewhat milder weather in the northwest, particularly Donegal and Derry, with highs about 4-7 C and possibly more sunshine than elsewhere, ” said forecaster Peter O’Donnell from meteotimes.net.
“The cold spell will moderate first in the coastal northwest.”
The rest of the week will stay unusually cold for the time of the year, with Met Eireann saying it will get colder the following week.
“During Friday, the trend will be for a band of mostly light rain to spread southwards across the country after a bright start,” said a spokesman.
“There are indications that next weekend will see abnormally cold conditions returning as northerly winds set in, bringing wintry showers and perhaps some snowfall.”