The Met Office says persistent heavy rain may lead to some disruption in Monmouthshire on Tuesday.
Forecasters said outbreaks of rain will spread across England and Wales during Tuesday. This will be heaviest and most persistent across parts of Wales, particularly over higher ground. Rainfall totals of 80-100 mm could accumulate over parts of Snowdonia.
The warning which covers Monmouthshire will be in force from 6am until 10pm on Tuesday.