The NWS has issued a FLASH FLOOD WARNING for the City of St. Louis until 6:00 pm. 
The National Weather Service in st louis has issued a
* flash flood warning for,
central st. charles county in east central missouri,
madison county in southwest illinois,
northern st. louis city in east central missouri,
st. louis county in east central missouri...
* until 600 PM CDT
* at 209 PM CDT, National Weather Service doppler radar indicated
numerous thunderstorms with very heavy rainfall across the warned
area. radar indicates up to 3 inches of rain have already fallen
in the metro area, with more on the way. very quick runoff can
be expected in urban areas.
* runoff from this excessive rainfall will cause flash flooding to
occur. some locations that will experience flooding include,
ballwin, bel-ridge, bellefontaine neighbors, berkeley, black
jack, brentwood, bridgeton, chesterfield, clarkson valley,
clayton, collinsville, cool valley, cottleville, creve coeur,
dellwood, des peres, edwardsville, ellisville, ferguson,
florissant, frontenac, glen carbon, granite city, hazelwood,
highland, hillsdale, jennings, kinloch, ladue and lambert
field.
Instructions:
Do not drive your vehicle into areas where the water covers the
roadway. the water depth may be too great to allow your car to cross
safely.
Address/Location
City of St. Louis Emergency Management
1915 Olive St
St. Louis, MO 63103
Contact
Emergency: 9-1-1