The sweltering heat endured by major American cities is being fueled by vast swaths of concrete and a lack of greenery that can ratchet up temperatures by nearly 9 degrees F (5 degrees C) compared with surrounding rural areas, new research has found.

In the past month, Phoenix experienced a string of four days above 115 F (46 C) for the first time and Boston hit 100 F for the first time in a decade. A deadly heat wave in the U.S. northwest, which scientists say would have been “virtually impossible” without human-induced climate change, baked Seattle at a record 108 F, while Portland, where roads buckled and power cables melted in the heat, reached an incredible new high of 116 F.

Read the full article about urban heat islands at Environmental News Network.