The soaring temperatures and humidity are expected to make life difficult for the European sides this summer, and Johnson is not sure if it is possible to be fully prepared for the conditions that await them.
"I don't think any of us know how hard it's going to be, or how hot and humid," the Liverpool defender told members of the press.
"We are trying to do a few things this end before we get there to try and prepare for it, but I don't think you can replicate it 100%.
"It's going to be difficult no matter how fit we are, or what we've been doing here, so we'll have to see how it goes in the game. Hopefully it isn't as hot as people think it's going to be."