A heat wave that has hit Phoenix hard this month has reached new, sweltering heights. The National Weather Service says the high temperature reached 100 degrees by mid-afternoon Thursday. It's a new record high for Oct. 27, beating the previous record of 98 degrees set in 2001. It also marks the latest date after summer that Phoenix has hit triple digits. The area's previous post-summer record for a triple digit reading was Oct. 23 in 2003. The state is in the midst of a heat wave that has made October one of the hottest in years, including lengthy runs of 90-plus degree days in Phoenix and Tucson that could break a record Thursday. National Weather Service meteorologists say a high-pressure ridge is the culprit.