Asked about specific humidity preparations, Gatland said: "We've been using wet balls and been using baby oil on them as well.
"We've taped them up as well, and we've already been through that process in the (training) camps we had before we've been away.
"We have been to two camps where one was at altitude and it was very hot in Switzerland, and then it was the late 30s in Turkey.
"We've done as much as we possibly can in terms of dealing with the heat.
"I think the humidity is going to be a factor. You can see how warm it is, but with the later kick-offs those temperatures are going to drop to about 20 degrees.
"It's going to be a lot cooler, but the challenge then is going to be the humidity and dealing with a slippery ball. It's how we cope with that.
"The players who have been to New Zealand will have experienced that. I come from Hamilton, where it's incredibly humid there.
"We know what it's like and we have players who have experienced a lot of night rugby, so we feel we've prepared well. We are looking forward to it."
Wales will hold an open training session at Kitakyushu Stadium on Monday, which is expected to be attended by hundreds of locals.
The players received a rapturous reception on their airport arrival, while banners and posters of support and Welsh flags are displayed throughout the city.
This article first appeared on RugbyPass.com and is republished with permission
