Among the signs of Lailatul Qadar is that it is a serene, quiet, shining night, neither hot nor cold but the temperate would be as if a moon is shining clear; it lasts until the break of the dawn. Rain may fall either during the night or during the day of that night.
Abu Huraira (Allah be pleased with him) reported: We were talking about Lailat-ul-Qadr in the presence of the Messenger of Allah (may peace be upon him) and he said: He who amongst you remembers (the night) when the moon arose and it was like a piece of plate (at the end of the month in a state of waning). (Sahih Muslim, Book 6, no. 2635).
Another sign is that at dawn, the sun rises without any radiant beams of light, appearing rather like the moon in its fullness.
Zirr b. Habaish reported: I asked Ubayy b. Ka’b (Allah be pleased with him): Your brother (in faith) Ibn Mas’ud says: He who stands (for the night prayer) throughout the year would find Lailat-ul-Qadr, whereupon he said: May Allah have mercy upon him; (he said these words) with the intention that people might not rely only (on one night), whereas he knew that it (Lailat-ul-Qadr) is in the month of Ramadan and it is the twenty-seventh night. He then took oath that it was the twenty-seventh night. I said to him: Abu Mundhir, on what ground do you say that? Thereupon he said: By the indication or by the sign which the Messenger of Allah (may peace be upon him) gave us, and that is that on that day (the sun) would rise without having any ray in it. (Sahih Muslim, Book 6, no. 2633)