[Update]: The ridiculously over-the-top shark RPG Maneater is free to grab until June 16th.
If you're looking for something to distract you from the scorching heat, at least for a little while, you'll be happy to hear that Wolfenstein: The New Order is currently free to grab. Simply head on over to the Epic Games Store, snatch yourself a copy, and you'll be good to go after a bit of a download.
The one catch, as always, is that the whole giveaway will only last a single week. As such, make sure to add a copy to your account before June 9th, after which you'll be able to play it whenever you want.
As for whether Wolfenstein: The New Order is even worth the trouble, I would say the answer is a definite yes. It's a solid shooter with a highly engaging story, and best of all, the whole thing is fairly short so it never overstays its welcome. So whether you're familiar with the setting or a complete newcomer, Wolfenstein: The New Order is absolutely worth checking out while it's still free.
Enjoy, and I'll leave you with one of the original trailers to help set the mood: