Frost and hard freezes are forecast for the next several days with cold Arctic air gripping much of southern Ontario.
Environment Canada said Friday that frost is likely again Friday night as temperatures drop to near or below O C, 32 F.
The weather agency said there's the risk of frost reoccurring nightly through Tuesday.
Preventative measures should be taken to protect frost-sensitive crops and plants that could be damaged or killed.
There is also the chance of flurries Friday night on gusty north-northwest winds with snow accumulations of two centimetres to four centimetres, an inch or more, possible.
Standing records for cold could fall Friday. A high of 4 C, 39 F, was forecast with the coldest high in Sarnia for May 8 being 4.6 C set in 1983. The record low in Sarnia for this date is minus 2.2 C in 1954. The mercury is forecast to drop to minus three.
Meteorologists said a polar vortex has pulled an Arctic air mass down from the north causing an extended period of significantly colder than normal temperatures.
The normal high for this time of year in Sarnia is 19 C, 66 F, with low temperatures usually around 7 C, 45 F.
