Unseasonably mild November weather made it the warmest Remembrance Sunday on record.
Temperatures reached a summer-like high of 21.2C in Porthmadog, Wales.
The Met Office described the conditions as “exceptionally mild”.
England and Scotland also broke records for the warmest Remembrance Day with highs of 19.2C in Bridgefoot, Cumbria, and 17.2C in Aviemore.
Castlederg in Co Tyrone saw a maximum of 16.5C, which was 0.2C below the record for Northern Ireland.
The Met Office tweeted: “It’s been an exceptionally mild day for most of us and the warmest #RemembranceSunday on record in the UK England, Wales and Scotland have all provisionally broken their previous maximum temperature records with Northern Ireland just 0.2°C shy of their record.”
The high temperatures this weekend followed the UK’s warmest Armistice Day on record.
On Friday, Myerscough in Lancashire enjoyed a high of 19.5C.