For a second consecutive day, dense fog blankets most of southwestern Connecticut early today, and increasingly warm, humid conditions has prompted the state to issue an air-quality alert.

When skies clear by midday, the National Weather Service predicts temperatures will rise to about 80 degrees, with a light southwest wind becoming south 5 to 10 mph in the morning.

The air-quality alert is in effect from 2 to 10 p.m. as ozone levels are expected to approach or exceed unhealthy levels.

Tonight, there is a 30 percent chance of showers and thunderstorms as the temperature dips to a low in the low-60s. There will be a south wind 5 to 7 mph becoming calm after midnight.

Tomorrow, there is a slight chance of showers and thunderstorms after 10 a.m. with a daytime high temperature in the low-80s and a southwest wind 6 to 9 mph. Chance of precipitation is 30 percent, the NWS says..

There is a 40 percent chance of showers and thunderstorms tomorrow night, with a low temperature in the mid-60s.

On Thursday, the NWS predicts a 60 percent chance of showers and thunderstorms, under cloudy skies and temperatures rising to a high in the low-70s. Nighttime showers and thunderstorms are also possible, with a low temperature about 60 degrees. Odds of overnight precipitation are 60 percent.

Friday brings mostly cloudy skies and a 50 percent chance of showers, with a high temperature about 70 degrees. Nighttime will be partly cloudy, with a low temperature dropping to the upper-40s.

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