The Labor Day holiday threatens to be a washout, the National Weather Service warns.

Rain, expected to start falling as a cold front moves into southwestern Connecticut this afternoon or evening, could be heavy at times, prompting the NWS to issue a flash flood warning.

The holiday day skies will likely be mostly cloudy for much of the day, with a daytime high temperature of about 80 degrees. The likelihood of rain -- possibly thunderstorms -- is 40 percent after noon, increasing to 70 percent tonight.

The temperature tonight will dip to a low of about 63 degrees as the cloud cover increases.

Tomorrow showers are also likely, the NWS says, with a high temperature of about 66 degrees. More precipitation is possible tomorrow night.

The outlook for both Wednesday and Thursday is also gray and wet -- there's a chance of showers both days with the temperature reaching the low-70s under cloudy skies.

By Friday, the weather service predicts, skies will clear and the temperature will hit a high of about 80 degrees.