The Met Office only issues them when meteorologists believe that dangerous, potentially life-threatening weather is expected imminently.
The areas under the red warning are forecast wind gusts of 90mph (144kmph) or more, which could lead to flying debris and falling trees, posing a danger to life, the Met Office added.
The winds are also expected to cause large waves, power cuts affecting mobile phone services, as well as damage to buildings and homes. Transport networks are also anticipated to be affected.
Heavy rain and strengthening winds will be felt across western parts of the UK from late on Friday.
This weather pattern will turn into Storm Darragh moving into Saturday.
The Met Office said the strongest winds would subside by late Saturday morning, but that it would remain very windy until the evening, with amber warnings remaining in place until then.
A yellow rain warning, indicating a risk of flooding, is also in place in parts of the western UK.