The yellow weather warning said commuters faced potentially longer journeys with bus and train services being affected and “spray and flooding on roads probably making journey times longer”.
The Met Office also warned of a “small chance of flooding to a few homes and businesses” and said “some interruption to power supplies and other services is possible”.
It said the weather warning, which covers the southeast of the country, would stay in place to 3am Thursday.
— Met Office (@metoffice) September 20, 2023
Forecasters said the heavy rain was the result of remnants of Hurricane Nigel sweeping across the UK from the Atlantic in the wake of Hurricane Lee which prompted flood warning in northern England this week.
Grahame Madge, from the Met Office, said: “On Sunday, we will start to see the influence of ex-tropical Hurricane Nigel, which will be offshore in the mid-Atlantic.
“These systems have a long reach, it will increase rainfall rates and also winds to bring unsettled weather to the UK.”
He added: “Although we’ve indicated that there could be flooding associated with the reasonably high levels of rainfall, that’s not something anticipated to be widespread.
“It’s something that may be a consequence of a catchment that suddenly gets more inundated or there are blockages in drainage.”
The showers can be linked to remnants of Hurricane Lee which brought over “moisture” and “higher temperature air” to the UK.
“It’s fair to say that it (Hurricane Lee) has brought more moisture with it, and also higher temperature air,” Mr Magde explained.
“When this air comes across us (the UK) it will deliver more in the way of rainfall than a normal system.”