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The weekend starts on an early sunny note, but the National Weather Service warns it won't stay that way on this last "official" day of summer.

Rain is verly likely to move across southwestern Connecticut later today -- along with possible thunderstorms by tonight.

Skies through late morning today will be partly sunny, but gradually cloud over as the daytime high temperature will be in the mid-70s.

By afternoon, clouds move in and, according to the NWS, there is a 90 percent chance of precipitation, with downpours and thunderstorms possible. The low temperature will be about 60 degrees.

Tomorrow, the first day of fall, showers and possible storms continue to be likely in the morning -- 60 percent odds. But the sun is expected to gradually emerge as the temperature rises to a high of about 70 degrees. Nighttime skies should fully clear, with the temperature tumbling to a low in the mid-40s.

Monday should be sunny with a high temperature in the upper-60s. Night skies will be clear, with a low temperature again in the mid-40s.

The outlook for Tuesday, according to the weather service, is sunny and temperatures in the 60s.