The region collectively experienced just under 35 hours of sunshine throughout the month, 41% of the October average.
This equates to a little over an hour of sunshine per day.
A week of “anti-cyclonic gloom” and the first named storm of the season contributed to the persistent grey skies and low cloud.
The figures were four hours short of the dullest October on record which was 31 hours in 1921.
Co Tyrone and Co Fermanagh faced the least sunshine with 31.1 hours and one and a half times its average rainfall.
Heavy showers also meant that Northern Ireland was the wettest part of the UK last month.
Around 155.5mm of rain touched down here, equating to 36% above the typical amount.
This was partly caused by Storm Amy hitting the UK on October 3 bringing 50-75mm rain to many areas.
The storm also brought gale-force winds and Northern Ireland’s strongest ever recorded October gust of 92mph at Magilligan, Co Londonderry.
As many as 65,000 homes experienced outages at the height of the storm, and 1,457 incidents were reported to the Department for Infrastructure, including fallen trees and flooding.
The impact also affected public transport, with speed limits in place on the railways following disrupted services.
Rainfall was very slightly below expected levels, with the UK receiving 99% of the long-term average for the month (121.2mm).
Levels varied across the country with Northamptonshire receiving only 60% of its typical amount.
The UK as a whole saw an average of 63.3 hours of sunshine lowest total for October in nearly 60 years, according to provisional data from the Met Office.
It is also the third lowest figure since comparable records began in 1910, with only 1960 (60.8 hours) and 1968 (56.8 hours) experiencing less sunshine during the month.
People face the rain during Storm Amy in October, Northern Ireland’s gloomiest October in over 100 years. Image: Pacemaker Belfast
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Dr Emily Carlisle of the Met Office said: “October 2025 has been the dullest October in almost 60 years for the UK.
“A week of persistent ‘anticyclonic gloom’, combined with unsettled autumnal weather and a named storm, made it only the second month this year, after February, to see below-average sunshine for the UK.
“Temperatures were above average for October, although not record-breaking, and rainfall for the UK falls just below average, although with much regional variation.”
Northern Ireland is expected to see similar conditions of wind and rain this week, although a Met Office spokesperson said things are expected to clear up by the beginning of next week.
The forecaster said: “In October, the conditions we had were obviously quite wet at times, but that persistent cloud really didn’t want to break. This week it does look quite similar.
“We’ve got spells of rain throughout this week up until Saturday. So between now until Friday, there will be rain at times – quite a lot of cloud in the forecast as well. But approaching the weekend and hopefully into next week, things start to look a little brighter.
“So from Saturday morning onwards, we should have some prolonged spells of sunshine, which will be quite a change.”
