Locally we’ve had a heat wave recently. The governments have advised people to stay indoors, stay hydrated and so on. So far, 16 people have died. Please. If you know someone who is elderly or very young, check in on them. Offer to drive them a coffee shop or a mall or somewhere with air conditioning for the price of a drink. People are dying needlessly.
With that out of the way, how do you run in this horrendous weather? Assuming this is NOT your first year of running, you stay hydrated and you run. Your body’s already adapted to both running and heat. If this is your first year, stay indoors and join the treadmill club. It's not worth it. If you are going to be running (or rucking) for over 45 minutes, get an electrolyte pack and toss it into one of your water bottles. A lot of the danger can be caused by imbalances (of course if you are regularly running for over an hour, you should have this in your recovery kit already).
Consider hats, sunglasses, and staying in the shade. Avoiding heat stroke will only lengthen your athletic career.