The two “cool” prayers are Fajr and ʿAsr. Fajr occurs during the coldest part of the night, and ʿAsr falls in the coolest part of the day after the sun has passed its zenith. Whoever faithfully performs these two prayers will enter Paradise—that is, safeguarding and properly establishing them is one of the means that lead to Paradise.
It is authentically reported that the Prophet ﷺ said, “You will see your Lord just as you see this moon.” The resemblance here concerns the act of seeing, not the object seen, for nothing resembles Allah. You will behold Him with a real, certain vision just as a person beholds the full moon on a clear night, while Allah is far too majestic and exalted for anything in creation to resemble Him.
At the end of that same hadith, the Prophet ﷺ said, “If you can avoid being deprived of the prayer before sunrise and the prayer before sunset, then do so.” The prayer before sunrise is Fajr, and the one before sunset is ʿAsr. These two prayers are the best of all the prayers, and the very best is the ʿAsr prayer, for it is the “Middle Prayer” about which Allah says, “Guard strictly your prayers, especially the Middle Prayer, and stand before Allah in devout obedience” (2:238). It is likewise authentically established that on the Day of the Trench the Prophet ﷺ said, “May Allah fill their homes and graves with fire for diverting us from the Middle Prayer—the ʿAsr prayer.”