Answer: Unfortunately, the answer to your question depends on not only temperature but also on soil type, exposure, rainfall and how long the plants have been in the ground. The best way to water is to water slowly so that the water can penetrate deep into the soil. This also allows you to water less often. Azaleas are relatively shallow rooted, but you do want them to root as deep as they can, so the soil should be moist down at least six inches.
The soil should be kept damp or moist but not sopping wet. The water can come from the garden hose or the rainfall. The soil's moisture holding capacity will depend on its structure. Unfortunately, the only way to tell is to dig down and see what is happening and then tailor your watering to that.
Newly planted azaleas grown with a fast draining soil mix in their pots may need frequent watering until the roots grow out into the native soil at which point the watering can become less frequent. Again, the only way to tell is to carefully dig down with your fingers or a trowel and see. In the very beginning, you may need to water that soil ball lightly every other day, then gradually wean the plants to a once a week watering when it doesn't rain. Make sure the surrounding soil is kept moist too because roots will not grow into dry soil.
Using several inches of organic mulch can help keep the soil cooler and more evenly moist. Do not exceed about three inches depth and do not allow it to touch the stems of the bushes.
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