While the rest of the group was facing a greater challenge, Clark was feeling better and better as he started to travel through the harsh rain. Professor Wright was strong enough from years of training that she easily saw through and withstood this storm. But she was amazed by how easily Clark resisted it.
The rain sometimes became caught in the wind so strongly that it felt like being hit by something solid. That wasn't even when small pieces of sleet or hail would be mixed in. While Brad and Ralph appeared to not care for the intensity, they were clearly weakened by it since it was constantly shifting.
The reason that Clark didn't feel much might have been his toughness overall, but Professor Wright knew that he had changed his meditation. She caught on to that easily since she had witnessed the training. But she still hadn't fully believed that he had created his own meditation technique.