The fourth and longest lasting heat wave of the summer continues and today is the fifth consecutive 90+ degree day. Today will also be the hottest day this week with high temperatures reaching the mid to upper 90s this afternoon, making it feel like it’s over 100 degrees due to the combination of high heat and humidity. As a result, heat advisories are in effect today for all of Connecticut, with excessive heat warnings in Hartford, Tolland and Windham counties.
In addition to the heat, coastal Connecticut is under an Air Quality Alert from 11 a.m. until 11 p.m. today for high levels of ozone. Ground level or “bad” ozone is created when two types of air pollutants, nitrogen oxides (NOx) and volatile organic compounds (VOC), react in the presence of sunlight and warm temperatures. These air pollutants are generated both inside and outside of Connecticut from industrial facilities and electric utilities, motor vehicle exhaust, and gasoline vapors. Air pollution is also transported into Connecticut on prevailing westerly winds from the Ohio River Valley and from the southwest, along the I-95 urban corridor from Washington D.C.
High pressure, located across the Great Lakes and New York state during the last couple of days, has slowly moved off to the south and east of Connecticut. The clockwise circulation around the high that had caused the wind from the northwest, keeping ozone levels low, has switched to west-southwest. This weather pattern will continue to transport heat and humidity into Connecticut over the next three days, which is conducive to the formation of very high levels of ozone pollution.
A strong cold front will end the seven day heat wave, as it moves across the region late Saturday with a band of showers and thunderstorms. A wind direction shift back to the northwest will usher in a cooler air mass on Sunday, putting an end to the heat wave and high concentration of ground level ozone.
Full forecast:
Today: Mostly sunny, hot and increasingly humid. Chance for a few afternoon thunderstorms. Heat index 100-105 degrees. High: Mid to upper-90s.
Friday: Partly cloudy, very hot and oppressively humid. Scattered afternoon storms, some strong. Heat index 105 or greater. High: Mid to upper-90s.
Saturday: Partly cloudy, hot and oppressively humid. Scattered thunderstorms. Any storm that develops could be strong to severe. High: Upper-80s and low-90s.
Sunday: Relief at last; mostly sunny, noticeably less humid, and cooler than recent days. High: Low to mid-80s.
Monday: Partly cloudy to mostly sunny, and less humid. High: Low-80s. Refreshing at night with a low temperature near 60 degrees.