Hail stones up to 1cm in size could hit parts of southern Scotland on Wednesday afternoon, forecasters have warned.
Thunder storms and torrential downpours are also likely in Dumfries and Galloway and the Borders.
The Met Office has issued a yellow warning of rain for the region from 16:00.
It could lead to localised flooding, with up to 30mm of rain expected to fall in less than hour, and as much as 60mm in three hours in some areas.
The storms are expected to develop after a largely hot and humid day in the south.
A spokesman for the Met Office said: "Some torrential downpours are possible leading to localised surface water flooding, with hail and frequent lightning also possible hazards.
"The public should be aware that there is a chance of some very localised significant disruption."
He added: "Large uncertainty remains regarding areas most at risk from storms, and many areas will miss these altogether and stay dry.
"However, where they do develop, very localised significant disruption is possible."