The UK's November temperature record has been broken, with 22.4C (72.3F) being reached in mid Wales.
The temperature was recorded in Trawsgoed, Ceredigion, on Sunday afternoon.
The previous record was also in Wales, where temperatures reached 21.7C (71.1F) at Prestatyn in 1946.
BBC Weather's Helen Willetts said: "It's a long-standing record that's gone and it could even be broken again on Monday."
The average UK temperature for November was between 10C (50F) in the North and 15C (59F) in the South, with the Wales average about 12C (53.6F), she added.
The record temperature had been caused by the type of air currently being experienced, with "mild southerlies and lots of humid air", the forecaster said.
Fog brought temperatures down in many areas on Sunday, but places which were free of fog saw temperatures in the high teens. The fog also led to some flights being cancelled at Heathrow.
More warm air is forecast for Monday but showers are due on Wednesday and Thursday.
The Met Office has issued a yellow warning for fog for much of England and parts of eastern Wales, from 21:00 Sunday until midday on Monday.
It said: "Areas of fog are expected to form during Sunday night becoming widespread and dense in places by Monday morning.
"Travel may be impacted by poor visibility, with some minor disruption expected."