Your body needs a couple of weeks to adapt to hot or cold weather. It can do this if the temperature goes up slowly over a month or so but problems arise when the temperature goes up 10C+ in one day. Then you feel it.
It's easy enough to deal with hot weather, just stay out of it. Stay indoors during the middle of the day. Keep the doors, windows and curtains closed to stop the heat coming in. Open the house up at night (if it's safe to do so) and let it cool down overnight, then close it up again the next morning when it starts to warm up again.
Minimise the use of electrical appliances so you don't add to the heat in the house.
If you have to go outside during the middle of the day, wear a broad brim hat or use an umbrella to keep the sun off you. You can also wear a long sleeve cotton shirt and soak it in water first, then go outside. As the water evaporates it cools you down. I used to stand under the shower in jeans, t-shirt and long sleeve shirt to get soaked then go outside to work or cycle.
Drink plenty of water when it's hot and avoid physical exertion where possible.
If you have animals, provide them with clean drinking water, shade and maybe turn a sprinkler on for them. Small animals and birds can be brought indoors during the heat of the day.
If this is going to become a regular feature, invest in shadecloth and hang it over your yard in spring, summer and autumn, or at least during summer. Encourage trees to grow to shade the yard too.
To help grass and plants deal with heat, don't water them too often in spring. Water them well once of twice a week and let them send their roots down into the soil in search of water. Then their roots don't get as hot and they have longer root systems that can take up more moisture from the soil. Don't cut grass too short because the grass leaf shades the soil and roots and stops them getting so hot. Cut the grass so it's 2-4 inches long in summer, shorter in winter.
If you are overheating or feel too hot, stand under a cold shower (wet your head too) for a few minutes and then stand or sit in front of a fan. If you wear a t-shirt under the shower it will hold more moisture and you cool off better when in front of the fan.