Alternative Version (more natural): Today is hot again, just like yesterday. After so many cold and rainy days, it feels great to finally enjoy some summer weather. But Japan’s summer is really humid, and going outside makes me feel exhausted. I’m trying to stay healthy so I don’t get sick from the sudden temperature changes. Tip: Use “had been” when describing a long past condition before a recent change (past perfect). “Sudden changes” is a clearer and more natural phrase than “big changes” when talking about weather. “Feel summer” is okay but “enjoy summer weather” sounds more fluent.