After early-morning patchy fog clears from parts of southwestern Connecticut, skies will generally brighten but air quality will be poor because of the heat and humidity.

The daytime high temperature will rise to the upper-80s, according to the National Weather Service, with a light south 5 to 9 mph.

The combined high heat and humidity has triggered an air-quality alert from state health officials, warning of unhealthy ozone levels from noon to 10 p.m. today.

Tonight will be partly cloudy, with a low temperature about 70 degrees and a south wind 3 to 8 mph.

Tomorrow, there is a chance of showers -- and thunderstorms -- during the day, under mostly cloudy skies and temperatures rising to the mid-80s. There remains a threat of rain and thunderstorms tomorrow night as temperatures dip to the low-60s.

Sunday should be mostly sunny, with a high temperature in the upper-70s, the NWS says. Nighttime will be partly sunny and a low temperature in the upper-50s.

The outlook for Monday, the weather service predicts, is sunny and temperatures in the mid-70s.