Answer: It's difficult to guess just when the weather might warm up and stay warm so you'll have to take your cues from the weather reports. Azaleas are generally safe when the weather is above freezing so when the nighttime temperatures remain above 35F, the plants should be able to endure the cold. Wait until then and have the cover ready to pop back over the plant if the temperatures are predicted to dip below that.
Best wishes with your landscape!
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