In the yellow weather warning for rain, the Met Office said, “slow-moving heavy showers may cause some localized rain.” flood and travel disruption”.
The warning is in effect from 1.08pm to 5pm and is located in parts of Dumfries and Galloway.
In a statement, the Met Office said: “This afternoon heavy showers with a chance of thunderstorms are slowly making landfall over parts of Dumfries and Galloway.
“By early evening the showers will tend to die out with drier conditions developing.
“In a few locations, 20-25mm of rain could fall in less than an hour, with a slim chance of 30-40mm in 2-3 hours.”
Heavy downpours will return on Monday, with a plume of up to 5mm of rain hitting Northern Ireland at noon and Scotland at 3pm.
The Hebrides and the west of Scotland will be hit by 5mm showers at 3pm with some parts of North East England and most of Northern Ireland getting between 1mm and 3mm showers.
At 9 p.m., showers of 5mm remain over the Hebrides, but the worst of the rain moves eastwards into the North Sea, with occasional showers over parts of northern Britain.
The Met Office said in its long-term forecast from Aug. 1 to Aug. 10, “Changeable conditions are expected for many at the start of the week, with outbreaks of light rain in central and southwestern parts.
“Meanwhile, mainly dry and clear conditions can occur in the north and many southern areas. The volatile regime will continue into the week, with clouds and outbreaks or rain likely in the west and northwest likely.
“It will become drier in the southeast, but here too some clouds or rain are possible. Temperatures are likely to be above average in the south and closer to normal in the north.
“Most areas may see some rain or showers towards the end of the period, although the southeast remains mostly dry with sunny or clear spells.
“Generally near normal temperatures for the north, maybe warm or very warm in the south.”