Met Office Shawbury said wind was expected to pick up on Friday along with outbreaks of rain.
Storm Callum has been upgraded from a yellow to an amber weather warning, which covers a large part of Pembrokeshire on Friday, October 12 and Saturday, October 13.
Gale force winds and torrential rain have begun striking both countries - but should skirt around the royal wedding in Windsor.
Storm Callum was striking parts of the United Kingdom on Friday morning with gale force winds of up to 76 miles per hour (120 kph) and torrential rain, leaving thousands of people without power across Ireland and the British Isles.
A Met Office yellow "be aware" warning for wind has been in place since 3am for the west of the country, with gusts of about 80mph expected. Northern Scotland could stay dry while the East of England could be seeing baking temperatures of 25C.
Forecasters are warning of more of the same over the weekend, although some parts of England will escape the worst.
While on Saturday there is a "danger to life" alert over potential flooding due to rain covering Lothian and Borders and Dumfries and Galloway.
'We have already seen this impact on the roads and we could see more flooding as the rain flows down from the mountains. "Making sure you know what the situation is like where you live is really important".
In Co Armagh, Trafficwatch NI reports that a the Tassagh Road, Keady is blocked by a downed tree, as is the Summerisland Road, Moy, the Kingsmill Road, Whitecross and the Loughgall Road, Portadown is partially closed due to fallen trees.
Met Eireann have said they are more than likely going to extend the weather warnings "as it will take a while for the winds to abate".