A sudden rise in temper- atures high above the Arctic is being monitored here for fear it could spark weather similar to 2018's big freeze.
The event, known as sudden stratospheric warming (SSW), can upset the polar vortex, which keeps icy weather moving in a predictable pattern around the North Pole.
When that happens it can disrupt the normal systems that influence winter weather in Ireland, Europe and much of the Northern Hemisphere.
An extreme example was the Beast from the East that paralysed the country in February 2018.
Met Éireann said it is too soon to know for sure how it might affect our weather.
The forecaster said the SSW could kick-start our typical mild winter weather pattern, which is currently held up in a cold spell.
"Every SSW is different and less than half lead to colder conditions in Ireland," it said.
"For example, the SSW in February 2018 led to the Beast from the East and Storm Emma, whereas the SSW in January 2019 had no significant impact here."
Confirmation of the SSW came just as Met Éireann issued its first extended weather forecast.
In a new service that began yesterday, a forecast for the month ahead is being issued every Tuesday and Friday.
The first one anticipates the continuation of the current cold, mainly dry spell for the rest of this week and much of next week, with temper- atures falling well below zero in parts of the west and north-west.
After that, a week of more unsettled and wetter weather with normal temperatures is indicated.
The remainder of the month and the start of February are expected to be wetter and probably milder than normal.