Some parts of Northern Ireland could see up to 40mm of rainfall on Wednesday, according to the Met Office.
Flood and heavy rainfall warnings have also been issued for parts of the Province.
Counties Antrim and Down are expected to see the worst of the heavy rain.
It will be cool at times with temperatures expected to be in and around nine degrees Celsius.
A break in the heavy rainfall is expected at around 5:00pm on Wednesday however road users are still advised to exercise caution as flooding is expected to still cause problems.
Temperatures are expected to drop close to freezing overnight and into Thursday morning.
Heavy rain is expected to return to Northern Ireland in the early hours of Thursday morning but will begin to clear in time for morning rush-hour.
Thursday is expected to be a much clearer day with some parts of the Province enjoying spells of sunshine.
The current Met Office weather warning is valid until 12:00pm.