The British world number one had to cope with strong winds after teeing off, then had to come off the course due to the threat of lightning before returning just half an hour later in surprisingly light breezes.
"I teed off this morning at 7:00 a.m. and it was a 25-mile-an-hour wind that lasted about 45 minutes," Donald said as steady rain swept across the 7,676-yard Ocean Course.
"Got called in for half an hour, came back out and the wind was completely different and just five miles an hour.
"Obviously the conditions are changing from hour to hour, and that's making it difficult on this course. With barely any wind, the course offers you some opportunities but under some tougher conditions, this is a very tough test."
A mixture of rain, thunderstorms, lightning and gusts up to 30 mph have been forecast for the year's final major which starts on Thursday with conditions expected to ease for Sunday's final round.
Suspensions in play are almost certain to be part of the package over the four days, though four-times champion Tiger Woods said this was nothing new for the players.
"We're so accustomed to them," the 14-times Major winner added. "Rain delays are part of summer months. As long as we get enough time to loosen up and warm up and get back into rhythm, that's fine.
"Sometimes it gets a little difficult when they keep you in the vans and you cool off and then they don't bring you in, you go back out. It's part of playing in the summer in the South."
The Pete Dye-designed oceanfront layout is no stranger to major events, having hosted the 1991 Ryder Cup and the World Cup in 1997 and 2003.
Stretched to 7,676 yards for this week's US PGA Championship, the Ocean Course is the longest layout to stage a major and its closing stretch is particularly formidable.
"The front nine is a really nice, playable golf course, and then the back nine is not," said Australian Adam Scott. "The back nine is very severe.
"There are good scores out there in good weather, but if the wind blows, it's just going to be very difficult, even if they move tees forward and stuff like that.
"The green complexes are very severe on some holes, and there is extreme penalty for a miss. There's water one side and big waste bunkers the other. It's certainly going to need some (good) ball striking."
World nunber two Woods, seeking his first Major title since the 2008 US Open, said he enjoyed the challenge of Pete Dye-designed courses.
"He makes you think, which I like, instead of just going out there and hitting a golf ball," the American added. "He makes you make a decision off the tees, makes you make a decision into the greens and makes you leave the ball in the correct spot.
"The thing about Pete is if you miss your spots, you're going to get penalised severely, and I think that's more so than any other course designer. But he gives you a lot of room."
One unusual aspect of this week's championship is that the Ocean Course will feature no bunkers, the PGA of America having declared all sandy areas as "through the green".
Consequently players will be permitted to ground their clubs in the sand, take practice swings and remove loose impediments.