According to NASA clouds are rare in the thin atmosphere of Mars, but usually form at its equator during its coldest time of year. Scientists noticed that last year — two years ago in Earth time— there were clouds beginning to form earlier than expected, so this year they were ready. via Technology and News Today https://www.theverge.com/2021/5/29/22460017/nasa-curiosity-rover-captured-images-clouds-on-mars