Today's climate is mild, isn't it?

The sentence "The climate today is very mild" is wrong.

First of all, climate is used to represent the climate of a place or a region, not to describe the weather of a certain day.

We usually say that the climate in Yunnan is mild, or that in Kunming is mild, not that the climate today is mild.

The climate is OK, which refers to a certain period of time, such as the climate at the vernal equinox, the climate in Tomb-Sweeping Day and so on.

If you want to express today's weather, you can directly say that today's weather is mild and the sun is warm.

Climate generally means that the temperature between zero and 15 degrees is mild, which usually refers to a wide range of specific places, not just today's metaphor.