The Met Office has upgraded a yellow weather warning to Amber in Northern Ireland as torrential rain has rendered some roads impassable.
The warning is in place until 7pm today, with heavy flooding already present in Dromore and Lurgan.
Motorists have been asked to avoid the underpass at Belfast's Stockman's Lane and the A1 southbound due to flooding.
Road users have described the weather as "biblical" and have been sharing photos and videos of the extreme conditions online.
Thunder lightening and flash flooding Susan Russam’s day out pic.twitter.com/wtfGaOioZq
— Susan Irvine Russam (@SusanRussam) July 28, 2018
This is the A1 Belfast to Dublin. Torrential rain causing severe flooding ????????⚠️
???? Kerri Truesdale pic.twitter.com/5XeJOftFuk
— Cool FM (@coolfm) July 28, 2018
— NI Greenways (@nigreenways) July 28, 2018
— Eugene Diamond (@EDiamond136) July 28, 2018
— Ryan (@RedBSierra) July 28, 2018
— Sarah Sherry✨ (@SarahSherry1) July 28, 2018
— Jessica (@Jessiew222) July 28, 2018
— Inspire Aerial Solutions (@I_AERIAL_S) July 28, 2018