As you might know, 饺子“Jiao3zi”means dumplings. 下“xia4”means down or Go Down as a verb. 下饺子”xia4 jiao3zi” in Chinese means to put the dumplings into the hot water and cook it. Just like the picture above. But in the Summer, most places in China are very hot. So if you hear people say 下饺子”xia4 jiao3zi”, it could be totally another thing!
Can you try to image what does it mean in this case? Actually, if you directly input下饺子”xia4 jiao3zi” in google search. You will get the answer. Or you can just click the link to have a look!