The humidex at Sarnia's Chris Hadfield Airport hit 47 C (117 F) at 3 p.m. Friday.
Environment Canada has a heat warning in effect and upgraded its severe thunderstorm watch for Sarnia-Lambton to a warning at 3:55 p.m. Friday. A severe storm moving rapidly east at 60 kilometres an hour was threatening southern Lambton County including Florence. The warning was ended at about 4:45 p.m. but the watch remained in effect.
Meteorologist Gerald Cheng said hot, humid air is coming up from the Gulf of Mexico.
"Everybody was complaining how cool it was in the spring and how rainy it was but finally we have some heat but it's getting to be unbearable now," said Cheng. "A cold front will come early Sunday and that's when we can expect to be able to breathe easier with more comfortable conditions."
High temperatures Friday and Saturday will be near record levels for Sarnia. The standing record for July 19 is 34.4 C set in 2013, and 36.6 C for July 20, set in 1987.
The hot, humid conditions are ideal for the development of potentially severe thunderstorms with strong wind gusts, large hail and heavy rain. Watch for updated alerts and take shelter if threatening weather approaches. In fact, there was a tornado warning for a while early Friday afternoon for parts of London-Middlesex. There have been no reports of any funnel clouds touching down.
The extreme heat forced the closure of the Children's Animal Farm at Canatara Park Friday for the well-being of the animals.
The St. Clair Region Conservation Authority issued a flood outlook statement Friday.
It says high water on Lake Huron, the St. Clair River, and Lake St. Clair has slowed the flow out of the Sydenham River creating high levels in flood-prone Wallaceburg.
The conservation authority said rain in showers and thunderstorms could result in minor flooding in floodplain areas, agricultural fields, and parks.
Residents are reminded to stay away from flooded areas and swollen streams and rivers.