The wild conditions, caused by a "weather bomb" over the Atlantic Ocean, may cause coastal flooding and affect transport, the Met Office has warned.
It will track eastwards across central Britain and the centre of the storm is forecast to exit from north-eastern England into the North Sea at around 10pm on Saturday.
Met Eireann claims Ireland will get very heavy rain and strong wind throughout today and tomorrow with western areas expected to bare the brunt of the storm.
"Gusts exceeding 50mph are expected widely within the warning area, with gusts of around 70mph along exposed coastal areas".More news: Man City v Napoli predictions: Champions League preview, line-ups & betting tips
Meanwhile, the HSE in the south-east says preparations are in place to react to the current and impending "Yellow" rainfall and "Orange" wind weather warnings associated with Storm Brian.
The strongest winds will hit the south west of Ireland and Wales early on Saturday morning, before heading east across the south of England. The Environment Agency's Alison Baptiste has warned the public to stay safe along the coast where there is set to be strong winds, large waves and some over-topping of coastal defences.
The Met Office has issued a yellow weather warning for high winds in Wales, the South West and the South on Saturday.
"Short term loss of power and other services is also possible".More news: Big Nintendo Switch update brings video capture and saved data transfers
"We urge people to stay safe along the coast and warn against putting yourself in unnecessary danger by taking "storm selfies" or driving through flood water - just 30cm is enough to move your auto".
A spokesman said: 'Fallen trees and other debris may temporarily block railway lines and damage overhead wires.
Drivers were also urged to take extra care on the roads during high winds, as vehicle recovery and insurance firm The AA reminded motorists that surface spray, reduced visibility and potential flooding remained high risks.
As Storm Brian moves away from the United Kingdom, it is forecast to bring heavy bursts of snow to the Alps and Norwegian mountains through Saturday night and Sunday.More news: USTR's Lighthizer says White House not actively working to withdraw from NAFTA