PORTLAND, Ore.—People headed to cooling centers Wednesday as the Pacific Northwest began sweltering under another major, multiday heat wave. Temperatures soared to 97 degrees Fahrenheit (36.1 Celsius) by the evening in Portland, Oregon. In a “worst-case scenario,” the temperature could reach as high as 111 F (44 C) in some parts of western Oregon this week before a weekend cooldown, the National Weather Service said. It’s more likely temperatures will rise to 100 F (38 C) or above for three consecutive days, peaking around 105 F (40.5 C) on Thursday. Sizzling weather also was expected in other parts of the country. The weather service said heat advisories and warnings would be in effect from the Midwest to the Northeast and mid-Atlantic through at least Friday. The high temperatures in Portland, part of a usually temperate region, would break all-time records this week if the late June heat wave had not …