A day after record rainfall, flooding remains a threat Monday in the Charleston area with showers, thunderstorms and astronomically high tides expected around 9 a.m., according to the National Weather Service.

A flash flood watch is in effect through Monday evening and could turn into a warning if the rain starts falling on the already saturated land.

Compounding the problem is abnormally high tides because the moon was on its closest approach to Earth this weekend, making its pull on the ocean waters greater - a phenomenon colloquially referred to as a "supermoon."

Even without the rain, the tides make coastal flooding a possibility.

In downtown Charleston, high tide was expected around 9 a.m., which coincides with the start of possible heavy rainfall, the Weather Service said.

Any low-lying areas are at risk for flooding, and authorities asked motorists to avoid them, if possible, and leave early for work Monday.

Between 1 and 3 inches of rain is likely, and isolated amounts of 5 inches are possible, according to the Weather Service.

Meteorologists reported 4.02 inches of rainfall at Charleston International Airport on Sunday, a record for that date. That nearly doubled the previous mark of 2.1 inches, which was set in 1970.

Here is the complete forecast:

Monday: Showers and thunderstorms, mainly after 9 a.m. Some of the storms could produce heavy rainfall. High near 89. Calm wind becoming northeast around 5 mph in the afternoon. Chance of precipitation is 90 percent. New rainfall amounts between 1 and 2 inches possible.

Monday night: Showers and thunderstorms likely, mainly before 8 p.m. Some of the storms could produce heavy rainfall. Cloudy, with a low around 76. Calm wind. Chance of precipitation is 60 percent. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tuesday: A chance of showers and thunderstorms, mainly after 10 a.m. Mostly cloudy, with a high near 91. Heat index values as high as 101. Light and variable wind becoming southwest 6 to 11 mph in the morning. Chance of precipitation is 40 percent.

Tuesday night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 76. Southwest wind around 9 mph. Chance of precipitation is 40 percent.

Wednesday: A chance of showers and thunderstorms. Partly sunny, with a high near 90. West wind 8 to 10 mph. Chance of precipitation is 40 percent.

Wednesday night: A chance of showers and thunderstorms. Partly cloudy, with a low around 74. Chance of precipitation is 30 percent.

Thursday: A chance of showers and thunderstorms. Mostly sunny, with a high near 88. Chance of precipitation is 30 percent.

Thursday night: Partly cloudy, with a low around 74.

Friday: Mostly sunny, with a high near 89.

Friday night: Partly cloudy, with a low around 75.

Saturday: Mostly sunny, with a high near 89.

Saturday night: Partly cloudy, with a low around 73.

Sunday: A chance of showers and thunderstorms. Mostly sunny, with a high near 88. Chance of precipitation is 30 percent.

Reach Andrew Knapp at 937-5414 or twitter.com/offlede.