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Hot Overnight Lows Keep Valley Residents From Feeling Relief

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Hot Overnight Lows Keep Valley Residents From Feeling Relief

The number of days when the temperature does not drop below 90° at night has increased greatly in the last several years. This is an indication of the urban heat island, a phenomenon of higher nighttime temperatures in the urban core compared to the surrounding rural countryside. A September 6 article in The Arizona Republic reported that the overnight low for Phoenix in June, July, and August 2010 averaged 82.8°, almost 3° above normal, and was the fifth-warmest nighttime average in 114 years of record keeping. When temperatures do not drop below 90° at night, nighttime temperatures provide less relief from the summer heat and air conditioners must run almost continually, increasing energy use. The overnight "low" at Sky Harbor Airport only dropped to 94° for three of the nights in July 2010.