Use the adjective scorching to mean extremely hot. The scorching heat from a wildfire tar on roads and char nearby houses and trees.
There's a huge difference between a warm day and a scorching one; the word implies a brutal heat. If the weather is scorching, you'll be desperate for air conditioning, iced drinks, or the relief of a cold shower. You can also use it to mean "harsh," like a critic's scorching review of a really terrible movie. Etymologists suspect that scorching is derived from the Old Norse skorpna, "to be shriveled."