Whether you’re in the US, the UK, or Europe, you are undoubtedly suffering through a heat wave. Here in the Southern US, we’re used to hot muggy summers, but this has been ridiculous! My backyard feels like a rain forest! The humidity has also been extreme, which can make for some dangerous conditions. Fellow gardeners (and others), here are some very helpful hints from the Old Farmer’s Almanac to deal with gardening and your own wellbeing in this weather: “Tips for Gardening in Extreme Heat.”
As for your plants, there are many good resources with guidance for keeping them alive during hot spells, like this guidance from British Columbia. In the US, every state has an agricultural “Cooperative Extension Service”, coordinated by the US Dept. of Agriculture, and many individual counties have their own branches. Your local extension service will be able to provide guidance specific to your particular area and local conditions. Stay safe and green!