The Met Office has issued a “yellow warning” of rain for the region, predicting localised flooding which could cause disruption to travel.
The persistent wet weather will last until tomorrow night with up to 2.76ins (70mm) of rain expected in worst-hit areas including parts of Lincolnshire, South Yorkshire and the Humber.
The Environment Agency (EA) also warned of a flood risk in the east, mainly from surface water and low lying rivers.
It said: “There may be some flooding of low-lying land and roads, some disruption to travel and possibly flooding to individual properties.”
Meteo Group forecaster Gareth Harvey said: “An area of prolonged rain is moving up over the eastern region and it’s not going to shift until Wednesday night.
“The rain is not exclusive to the east region but that’s where the persistent and largest rainfall totals of between 50 and 70mms will be.
“Pretty much the whole of Great Britain will see rain at some point over the next 48 hours.
“This means there could be some localised flooding.”
The EA has issued 10 low-level flood alerts in the South East and the Midlands, mainly warning of groundwater flooding close to rivers.