Ayurveda calls this stretch of the year Varsha Ritu, the unsettled, rainy late-summer season running roughly mid-July into mid-September, and it is unusually precise about what governs it.

The defining event is Vata aggravation. Vata is the principle of air and movement, responsible for circulation, nerve impulse, breath, thought, and the timing of all of it. Its qualities are dry, light, cold, mobile, and irregular. The classical texts describe Vata as accumulating quietly through the dry heat of high summer and then becoming openly aggravated once the weather turns changeable and damp, which is exactly what late August does here.

Vata's qualities, mobile, irregular, light, and most active in the latter part of the night, are the ones the classical texts associate with disturbed sleep. Contemporary Ayurvedic practitioners commonly map that to the pattern described above: not difficulty falling asleep, but difficulty remaining asleep, with an active mind and an inability to return.

There is a second factor. The classical texts describe Agni, the digestive fire, as diminished during this season. A heavy or late dinner that your system managed comfortably in May sits undigested in August, and undigested food, in this framework, is one of the more reliable ways to disturb the second half of the night.