It's shaping up to be an intensely hot week over parts of Central Canada, as southern Ontario and southwestern Quebec face a possible heat wave.
Temperatures are expected to rise "well into the thirties," Environment Canada forecasts, with the humidity making it feel like 40 C or more.
"This will make for very uncomfortable conditions," the federal weather agency said in a special statement for Ontario covering a band from Windsor to Ottawa.
"It is advised to stay in an air conditioned place or seek shade when possible, drink plenty of water and limit physical outdoor activity."
The heat will drift to Ottawa and Quebec's Gatineau region by Wednesday.
"Nighttime temperatures will not drop below 22 C for many, so some uncomfortable days and nights are ahead," CBC meteorologist Johanna Wagstaffe said.
Further into Quebec, the area from Val d'Or east to Trois-Rivières will be affected, with temperatures solidly in the high 20s midweek and a few days above 30. Montreal could see a peak of 33 C on Wednesday and Thursday.
The heat will reach as far as the East, with Fredericton and St. Stephen, N.B., forecast to reach 30 C on Wednesday.
"Basically, from southern Ontario to the Maritimes will be hitting the 30s over the next two to three days, though southwestern Ontario will see the longest of the heat event," Wagstaffe said.
She said humidity warnings will probably be issued in Ontario as the humidex rises above 40 C, and possibly in Quebec as well.
Individual cities can also disseminate heat alerts, triggering relief measures. If Toronto issues one, it would be the city's third of the season.
Montreal public health officials said they expect a heat warning as early as Tuesday. Norman King, an epidemiologist with Montreal Public Health, advised people to seek out air-conditioned spaces, reduce physical effort and drink a lot of water during the extreme heat. King said vulnerable groups like the elderly and people with respiratory problems should pay particular attention to these measures.
CBC Ottawa climatologist Ian Black counselled residents of the national capital to "find a cool spot" to evade the heat. "Air quality may also decline, and there may even be some thunderstorms at times," Black said.
A cold front will finally blow in on Friday to provide some relief in southern Ontario, while Quebec will see the heat persist through Friday, Environment Canada said.
A heat wave in Ontario is defined as three days of 32 C or more; in Quebec, it's three days of 30 C or higher.
Flood warning in B.C.
Elsewhere in Canada, two low-pressure systems over the Prairies could bring severe thunderstorms to southern Manitoba and Northern Ontario on Monday afternoon, while a flood warning and flood watch are in place for parts of British Columbia.
Most of the Prairies have a risk of rainstorms for Monday, but Manitoba-Ontario border is in line to see the brunt of it. Alberta is also expected to be doused by widespread rain showers.
In B.C., a rainfall warning for the Interior has been lifted, but river levels across much of the region were still rising quickly due to the weekend's precipitation plus rapid snowmelt.
The province's B.C. River Forecast Centre said the Shuswap River was rising two centimetres per hour in the village of Lumby on Sunday afternoon, and placed a flood warning on parts of the waterway. A flood watch was in place for other stretches of the river, as well as the North Thompson and South Thompson rivers and the Cariboo region, where up to 50 millimetres of rain fell Saturday and Sunday.