Spray and sudden flooding in the impacted regions could lead to difficult driving conditions and some road closures.
There is also a slight chance power cuts could happen.
The advisory is in effect from 9.42am until 11pm and covers several areas across the southeast.
The warning reads: “Heavy showers already affecting the south and east of the Isle of Wight will become more widespread across the warning area through the afternoon, with some thunderstorms also developing.
“These may be quite slow-moving and last for an hour or two.
“Some torrential downpours are possible with a few places seeing two inches (50mm) of rain or more within a few hours.
“Lightning and hail are also additional hazards.”