A heat wave will lift parts of Maine into the mid-80s Wednesday, pushing the mercury well past the average temperature for May 2. By late afternoon, Bangor is expected to reach 83 degrees — the same highs predicted for Portland and Augusta, according to the National Weather Service. Similarly dry, hot temperatures will be felt across the southern portion of the state, as a mass of high pressure, warm air moves in from the south, said Tom Hawley, a weather forecaster in Gray. “It’s going to feel like mid-summer heat today,” Hawley said. The last time Maine hit 80 degrees was on Sept.