 The complex of refining and chemical companies is called Chemical Valley and located south of downtown Sarnia . The city has the highest level of particulates air pollution of any Canadian city because of its reliance on the petrochemical industry . About 60 percent of the particulate matter , however , comes from the neighboring United States . Lake Huron is cooler than the air in summer and warmer than the air in winter ; therefore , it moderates Sarnia 's humid continental climate , which makes temperature extremes of hot and cold very rare . In the winter , Sarnia experiences lake @-@ effect snow because Arctic air blows across the warmer waters of Lake Huron and condenses to form snow squalls once over land . 
 The complex of refining and chemical companies is called Chemical Valley and located south of downtown Sarnia . The city <a href='got' title='1'><mark>has</mark></a> the highest level of particulates air pollution of any Canadian city because of its reliance on the petrochemical industry . About 60 percent of the particulate matter , however , <a href='uninflect' title='2'><mark>comes</mark></a> from the neighboring United States . Lake Huron is cooler than the air in summer and warmer than the air in winter ; therefore , it <a href='uninflect' title='3'><mark>moderates</mark></a> Sarnia <a href='null_genetive' title='4'><mark>'s</mark></a>humid continental climate , which <a href='uninflect' title='5'><mark>makes</mark></a> temperature extremes of hot and cold very rare . In the winter , Sarnia experiences lake @-@ effect snow because Arctic air <a href='uninflect' title='6'><mark>blows</mark></a> across the warmer waters of Lake Huron and <a href='uninflect' title='7'><mark>condenses</mark></a> to form snow squalls once over land . 
Da complex of refining and chemical companies is called Chemical Valley and located south of downtown Sarnia . The city got tdahighest level of particulates air pollution of any Canadian city cause of its reliance on thdaetrochemical industry . bou 60 percent of the particulate matter , however , come from the neighboring United States . Lake Huron is cooler than the air in summer and warmer than the air in winter ; therefore , it moderate Sarnia  humid continental climate , which make temperature extremes of hot and cold very rare . In the winter , Sarnia experiences lake @-@ effect snow because Arctic air blow across the warmer waters of Lake Huron and condense to form snow squalls once over land .