Moving to Kumagaya, is the heat really that different?

I’m moving due to my husband’s work. I’ve heard that Kumagaya is the hottest place in Japan, and our apartment consultant was bragging about it. But, is it really that different? My husband lived in a different place in Saitama for most of his life, and he said “It’s probably not that different”. And for the last couple years we lived in Kisarazu which was pretty nice weather wise, but does anyone who actually lived in Kumagaya and other places in Japan feel an actual difference?