The complete sentence is "Cut the grain to feed the old cows before the summer heat", which means: If the millet doesn't sprout in the summer heat, it will be confiscated, just like useless weeds, so it can only be cut and fed to the cows.
Folk proverbs related to summer heat:
1, it's still hot in summer, like an autumn tiger.
2, it is not hot in summer, and it is hot at noon.
3, hot cooked valley, solid grain drum.
4. Rain in the early summer, rice in the barn.
5, if it doesn't rain in the summer, even if it is difficult to protect rice.
6, three days in the summer (late rice) is pregnant, and the cold dew comes to the rice.