The Met Office has issued a thunderstorm warning for Northern Ireland.
A yellow alert - meaning disruption is expected - comes into force in the early hours of Monday and lasting the entire day and all of Tuesday.
The Met Office, however, said while some places will likely see "severe" thunderstorms, there is significant uncertainty in location and timing.
"Areas of thunderstorms are increasingly likely to develop over the south of the UK or nearby continent late in the weekend or early next week, and will generally track north or north-westwards, potentially affecting all parts of the UK," The Met Office said.
"Whilst the most intense thunderstorms, in some instances associated with large hail, will most probably be those triggered by the high temperatures of the day over England and Wales, other areas of storms producing heavy rainfall and frequent lightning could reach further north at times over Scotland and Northern Ireland.
"These could occur at any time of the day. Of the area highlighted, at present the west of Northern Ireland and west of Scotland seem less likely to be affected than other areas, but still could not be ruled out. Where the storms occur, rainfall totals of 30-40 mm could fall in an hour, with some locations potentially receiving 60-80 mm in 3 hours, although these will be fairly isolated."
Forecasters are warning of the potential of flooding and damage to building, power cuts and travel disruption.
Temperatures on Friday are expected to hit 22 degrees in NI although it could be much hotter in southern regions of the UK.
Clear skies are expected into the evening with the weekend expected to be dry with sunny spells.