Farther to the east, Ireland and the United Kingdom are also watching Ophelia's track, which could bring hurricane conditions to some areas there early next week.
The hurricane center's five-day forecast, which can change, has Ophelia heading toward the British Isles by Monday.
It is now around 760 miles south-west of the Portuguese Azore islands, whipping up 75mph winds as it trundles eastwards.
"There is a lot of uncertainty as to the exact evolution and movement of this weather system during the coming four days, but storm-force winds, outbreaks of heavy rain, and very high seas are threatened".
Met Office forecaster Alex Burkhill said: "Ophelia became a hurricane overnight and the forecast track takes it eastwards towards Iberia for the weekend".More news: What Does Mental Health Mean To You?
Ophelia is forecast to hit Ireland and the south-west coast of Britain at about 1am BST, before moving up to the northern-most tip of Scotland by 1pm.
The storm will coincide with the 30th anniversary of the Great Storm of 1987, which hit southern England on October 15 1987, costing an estimated £1 billion and claiming 18 lives. The last time a season produced 10 consecutive hurricanes was in 1893, according to Colorado State University meteorologist Phil Klotzbach - a period when tracking hurricanes largely relied on ships and barometric readings.
Western Britain will also likely be battered by gusts of between 60mph and 70mph.
Met Éireann says it's hard to predict the exact path of the hurricane but at the very least Monday will be a windy day with spells of rain.
The unsettled weather looks likely to continue into Tuesday due to a separate band of low pressure, and will remain changeable throughout the rest of the week.