“Hizashi” (日差し) is a rather interesting word probably best translated as “sunshine” or “sunlight”. For example, “yowai hizashi (弱い日差し) is “soft sunlight”, while “aki no hizashi” (秋の日差し) is “autumn sunlight.”
This being summer, the phrase “hizashi ga tsuyoi” (日差しは強い) - the sunlight is glaring - is quite common. I’ve lived in many places as hot as Japan, but nowhere where the 日差し is so 強い. (This may be why Japanese tend to have very thick eyelids and narrow, dark eyes - all of which I lack.) I’ve noticed that neither my dog nor I are much affected by the heat, but we’re both quite affected by the 日差しの強さ.
Stifling weather is expected to continue in Kumamoto for the foreseeable future. My advice is to stay out of the sun. - William