A severe weather warning for heavy rain that could flood roads and campsites across the west coast tomorrow and on Friday was issued by the Met Office today.
The yellow – “be aware” – alert for today and tomorrow will see up to 100mm (4in) falling widely, and 150mm (6in) over mountains.
The warning area covers the entire west coast north from Inveraray in Argyll, including Mull and Skye.
It remains in force from today until 6pm tomorrow.
The rain warning follows winds which reached 68mph battering Scotland last Sunday.
Further unseasonable conditions followed yesterday when motorists had to scrape frost off their windscreens in areas such as Aberdeenshire.
BBC weather presenter Simon King tweeted a photograph from Auchleven, near Insch.
He said: “Frost in August? You bet! Bit of car windscreen scraping in rural Scotland this morning...”
The Met Office said the heavy rain would continue for more than 24 hours.
A spokeswoman said: “Across the north-west Highlands and north-west Argyll, persistent rain will turn heavy and continue through much of Thursday and well into Friday.
“Driving conditions are expected to deteriorate, with localised flooding on prone sections of road.
“The persistence of the heavy rain may also affect outdoor events and holiday camping activities in these areas.
“The rainfall is expected to ease later on Friday.”
The agency said the downpours would be caused by a strong and very moist westerly airstream which was expected to cover Scotland from last night until Friday.
The spokeswoman said: “As this encounters the mountains of north-west Scotland, large amounts of rainfall are expected.
“Through the whole period, rainfall totals of 50-100mm (2-4in) are expected widely, with 150mm locally over the mountains.
“There remains uncertainty regarding how long the heavy rain will last into Friday.”
CalMac said ferries between Mallaig, Skye and South Uist may be cancelled.
The Scottish Environment Protection Agency (Sepa) has issued two flood alerts.
One covers the Fort William, Mallaig and Ardnamurchan areas, and Skye and the Small Isles. The other, further up the west coast, stretches from Kyle of Lochalsh to Lochinver, including Applecross and Torridon.
A Sepa spokesman said: “Heavy and persistent rainfall has been forecast which will lead to a risk of flooding from rivers.
“Possible impacts may include localised flooding of land and roads, especially in known trouble spots.
“Wet road surfaces may lead to travel disruption and longer journey times.”