Hello, Team AstraQom!
My wife tells me the weather in Ontario has been miserable. I am certain a "dyed-in-the-spandex-and-tech-fiber" guy (who has lived in Florida for 25 years) might not think it so bad, but hot is hot no matter how you look at it. If the weather is too warm during the time you originally planned to walk or run, see if you can adjust the time you walk or run to the earliest hours of the morning or latest hours of the evening you can tolerate.
Our Sunday morning group, "The Breakfast Club," meets as late as 8:30 in the morning during the winter months...we slowly slide the time toward 7:00 a.m. as the weather becomes more warm and humid here.
If you can't change the time because of your work or family commitments, then ease up on the intensity and let your body adapt to the conditions. Remember the focus is on endurance right now. By now I hope you've developed a habit of (near-)daily walks and runs. It usually takes three weeks to develop a habit, and six weeks or more to see physical change as the result of that habit. You might ask, "do I need to think about speed work?"
My answer is 'not necessarily.' New runners, young runners, and runners who are older, will develop and maintain speed by just getting out and running. Adding a little more time as your body tolerates the walk or run develops endurance, which translates into speed when it comes time to do a (shorter) race.
Think about it: If you, over the course of a year, learn to run at a comfortable pace for six to eight kilometers, and your race is a 5K, your body will most likely look at that as a simple accomplishment. You've run more than five kilometers at a time for weeks and weeks, so you'll feel like running the race a little faster than your normal run.
I've had many runners come visit my training sessions in the past. They felt the need to learn to run faster before they learned to enjoy just plain running. Naturally, they were overwhelmed by seeing more-experienced runners blast by them, without realizing the very same folks who were making them look foolish were first-time runners only years before.
So, this week and in the future I want you to focus on the long run. Train for the distance you want to run. The speed will show over time...and with a lot less pain than what I endured as a new runner.
Have a safe, mileage-filled week!