Yellow weather warnings for wind and rain are in place for parts of Devon, north Wales, northern England and southern Scotland, meaning these areas could continue to receive significant amounts of rainfall.
Much of the United Kingdom will experience some heavy rain on Friday, with further spells at times during Saturday, as Storm Callum passes to the north west of the UK.
He warned that gusts of up to 40 or 50 miles per hour will be felt across western parts of Scotland, Wales, and western England throughout the day, with stronger gusts of 60 miles per hour possible along the Irish Sea coast.
There was also bad news for commuters in south Wales, with Arriva cancelling a number of train services for the morning due to the high winds and heavy rain.
So far, Galway has escaped the brunt of Storm Callum - with no reported power outages or major obstructions on the road network.
The main impacts for the United Kingdom will be from heavy rain across some western areas on Friday and Saturday.
Chief Meteorologist at the Met Office Frank Saunders, said: "Strong winds at this time of year can increase the rate of leaf fall which can potentially block drains or culverts".
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On Tuesday, heavy rain caused widespread floods and landslides in parts of Scotland. There are also reports of a fallen tree at the Milltown Road, Belfast.
Here, Clare County Council has held meetings involving various responders as they monitor the expected situation locally.
Train cancellations will affect those travelling the Shrewsbury to Aberyswyth line through Mid Wales all weekend.
It is because the storm is likely to coincide with high tides around the south Wales coast.
The deluge poses a risk of communities being cut off by flooding.
NRW has also advised people to take extra care will driving, to avoid walking or driving through any flood water, and to avoid fast flowing rivers and streams.
Winds of up to 70mph are sweeping across the United Kingdom and Ireland on Friday.