The Met Office has issued a yellow "be aware" warning of ice for Denbighshire, Flintshire, Powys, Wrexham and Monmouthshire.
It says there could be difficult driving conditions in places.
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Calls graded as 'amber' have no target response time. Now a planned review of the category is underway.
Carwyn Jones will try to focus Labour members' attention on their party's achievements in Wales in what could be a tense conference.
Much of Wales again enjoying a fabulous day with warm sunshine! A little cooler in the west where the mist and low cloud will linger!