A Status Orange weather warning has been issued for the entire country today.
The warning was sent out by Met Eireann at 2am and will remain in place until 10am this morning.
"Fog will be fairly widespread this morning, most dense inland, away from coastal areas, leading to poor driving conditions," it reads.
Today will be cold, with top temperatures of 3 to 7C across the board but 8 to 10C in southern coastal counties.
It's going to be frosty in the morning, and the fog is likely to linger in some places until the afternoon.
Tonight is set to be freezing - as low as -2C.