Hostas have been known to tolerate severe drought conditions but they really prefer about an 1” (2.5cm) of water per week during the growing season. This is especially important for the lighter type or sandy soils. Moisture is easily lost through foliage so it’s important to make sure the water penetrates deeply into the soil to develop a good root system. Too little water can cause a mild burning of the leaf tops.
If your hostas do not get enough water, leaves will droop, but hostas are tough and usually endure. Over a dry period hostas simply stop growing. If possible, ensure that your hostas are kept well-watered.