Abu Tharr Al-Ghefari said: "The Messenger of Allah, salla Allahu alaihi wa sallam, said "O Abu Tharr! if you fast three days of every month, then fast the 13th, the 14th and the 15th ".
[at-Tirmithi; Sahih]
Abu Said al-Khudri reported that the Messenger of Allah, said: " No servant fasts on a day in the path of Allah except that Allah removes the Hell Fire seventy years further away from his face."
[Bukhari and Muslim]
Abu Tharr Al-Ghefari said: "The Messenger of Allah, salla Allahu alaihi wa sallam, said "Whoever fasts from every month three days, it is like fasting the whole year "
[Ibn Majah and at-Tirmithi]
So my dear brother fast an extremely hot day, to avoid an even hotter day .. and prepare yourself for a time when no food or water will be there.