High pressure is building across the UK and this means the weather will become more settled with brighter conditions.
After a chilly start on Monday morning, with sunshine and light winds across much of England and Wales, temperatures will climb into the low 20s.
Even with more cloud in Scotland and Northern Ireland, it will turn warmer with highs also reaching 18 to 22C.
It will also start to feel more humid again.
That more humid air combined with light winds across England and Wales into Tuesday means it will start off rather misty and foggy with areas of low cloud for some.
Once the sun has broken through though, it will feel warmer still.
Temperatures could peak at around 24 or 25C in south-east England, but reach the low 20s Celsius in many other parts of England, Wales, Northern Ireland and Eastern Scotland.
The highest temperature though will be determined by how much the cloud breaks allowing the strong September sunshine through.
2026 has already been a record-breaking year for the number of days above 25C, with last week exceeding the record of 89 days set in 1959.