If your Canada Day long weekend plans include a cold body of water or air conditioned spaces, congratulations.

Everyone else is in for a world of hurt, according to meteorologists, as temperatures soar well above 30 C on both Saturday and Sunday.

With humidity in the mix, it could feel as warm as 42 C outside on Saturday. On Sunday, humidex values will take us all the way up to a soupy 43 C as an "extended heat wave" takes hold across Southern Ontario.

Weather Network meteorologist Dr. Doug Gillham says that this dangerously hot weather should persist through the first (and possibly second) week of July, forming what will likely be the hottest stretch of 2018.

Great news for heat seekers, I guess, but the transition from relatively cool (as in this past weekend's temperatures) to scorching hot won't be a peaceful one.

"Periods of rain and thunderstorms are likely for Wednesday," says Gillham. "Strong storms are possible (especially east of the GTA) with locally torrential rain."

Spectacular weather today & Tuesday - sunny, low humidity & lower 20s. Periods of rain/T'storms Wednesday w/ localized torrential rain; Heat builds Thurs & Fri; Very hot & oppressive humidity for Canada Day long weekend; Humidex in the 40s; More details: https://t.co/j739Z9FHW9 pic.twitter.com/LtbCeam8D1 — Doug Gillham (@gtaweather1) June 25, 2018

After that, it's sunshine galore as a low pressure system brings heat and humidity into the region from down south. Monitor Toronto Public Health closely for extreme heat warnings and directions on how to stay safe.

The extended heat wave will begin late this week, according to forecasts, with temperatures spiking from 20 C to 29 C between Wednesday and Thursday.

"Enjoy the cooler temperatures while they last," says Gillham. And stock up on sunscreen, please and thank you. You'll definitely need it if you step foot out of the shade at all this Canada Day weekend.