What does it mean to be warm in spring?

First of all, you should know that the vernal equinox is a solar term.

Equinox: It starts on March 20th (or 2 1) and ends on April 4th (or 5th) every year. The vernal equinox begins on March 20 or 2 1 day of the solar calendar every year, and the sun reaches 0 degrees of the yellow meridian (vernal equinox). The length of day and night is average, just half of the 90th day of spring, so it is called "vernal equinox". On the vernal equinox, the sun shines directly at the equator, and day and night are almost equal. Then the direct sunlight position gradually moved northward, and the days were long and the nights were short. The vernal equinox is an important solar term, which not only has astronomical significance: the northern and southern hemispheres are equally divided day and night; Climatically, there are also obvious characteristics. On the occasion of the vernal equinox, China has entered a beautiful spring scenery except the Qinghai-Tibet Plateau, the northeast, the northwest and the northern part of North China. On the vast land, willows are green, Fei Ying grass grows, wheat jointing and rape blossoms are fragrant.

In fact, in April, the climate in most parts of the country is getting warmer and warmer, and some areas are even very hot.

So there is this sentence: spring is neither warm nor warm to describe climate change.