A Status Yellow fog warning remains in place this morning for the whole of Ireland.
Met Eireann said in its weather warning that the fog will be "slow to lift and will linger in some parts for much of Saturday".
It added that fog will become "widespread and dense again on Saturday evening, but retreating to northern areas by Sunday morning".
The message is valid until 9am on Sunday morning.
Otherwise, it will be largely dry with sunny spells and just the odd light shower, forecasters said.
Met Eireann says showers will become a little more frequent along western and southern coasts later today.
Highest temperatures of 5C to 8C, but lower where fog lingers.
Showers near the western coasts will spread inland this evening and tonight, with lowest temperatures of 1C to 4C with a touch of frost.
Then Sunday will bring a mix of sunshine and showers, with remaining mist and fog patches in the east and north clearing during the morning.
The showers will be most frequent in the west, with a few of them heavy. Light to moderate west to southwest winds will increase fresh to strong and gusty near west and southwest coasts. Highest temperatures of 6C to 8C.
Met Eireann's national outlook for Christmas week is as follows: "A mix of clear spells and scattered showers on Sunday night with lowest temperatures of 3 to 6 degrees in moderate westerly breezes.
"Monday is looking to be mainly dry with sunny spells. Towards evening rain may develop in the south. Highest temperatures of 7 to 9 degrees in moderate westerly breezes. Good clear spells will develop on Monday night. Minimum temperatures of -1 to +3 degrees with a patchy frost.
"Tuesday, Christmas Eve is looking largely dry as well, though again, there is a chance that rain develops in the south. Highest temperatures of 5 to 8 degrees. The night before Christmas will probably be a cold one with widespread frost and temperatures as low as -2 or -3 degrees.
"Current indications are that Christmas Day will be largely dry with some sunshine and only light winds.
"However, latest indications also suggest that wet and windy weather will develop later on Christmas Day, in the evening or early night.
"This will then be the start of a more unsettled period of weather for the days after Christmas with spells of wet and sometimes windy weather."
