The warning was issued on Friday morning by the Scottish Environment Protection Agency (SEPA) and has been reinforced today with the message that people should take care while out and about.
The agency said that heavy rain would fall overnight and continue into Saturday morning, a statement said: “There is a risk of localised flooding of low lying land and roads from smaller watercourses and surface water.
"At this stage the greatest risk is in the East of the area."
The flood warning is in place until further notice. Advice and information on how to protect yourself and your property is available through Floodline by calling 0345 988 1188.
The Met Office has predicted that the weather will start to brighten up as Saturday goes on, with sunny spells potentially breaking through in the late afternoon.
The highest temperature the area will see is 18C however light northerly winds will keep a chill in the air.
Sunday will feel slightly more like summer with a dry day forecast and temperatures climbing to 20C. Sunshine is expected with only a light breeze.
Into next week, some light and patchy rain is forecast around the east coast from Tuesday, but for most across the Lothians it will remain dry and sunny with some light wind.