Where does the idea that Gehinnom is a “hot” place come from? The only source I know of is a Christian one (i.e. fire and brimstone, etc). Our ideas are much different (unless someone can provide an authoritative source to the contrary). If anything is a hot place, it is Olam Habah, as follows:
The temperature of heaven can be accurately computed. The authority is Sefer Yeshaya (Perek 30 Passuk 26) which says, “Moreover, the light of the moon shall be as the light of the sun, and the light of the sun shall be sevenfold as the light of seven days”.
Thus, heaven receives from the moon as much radiation as the earth does from the sun, and in addition seven times as much as the earth does from the sun, or eight times in all.
With this data we can compute the temperature of heaven. The radiation falling on heaven will heat it to the point where the heat lost by radiation is just equal to the heat received by radiation. In other words, heaven loses eight times as much heat as the earth by radiation. Using the Stefan-Boltzmann fourth power law for radiation:
(H/E)^4 = 8