So nearly right. There is evidence that the southern ice cap on Mars “melts” every summer. Except that it sublimates, meaning turns straight to vapor because it is CO2 and not water, that it does so at a ridiculously low temperature, and that it reappears during the winter. In other words, it is cyclical. https://mars.nasa.gov/resources/22192/the-changing-ice-cap-of-mars/As for your other contention, the climate has changed many times, but on a scale of thousands of years, not 200. Change has never been seen at this rate. There is actual science out there for those interested.
Midsummer and Midwinter referred to the solstices in earlier times.