North winds gusting over 20 mph on Monday delivered the chilliest air of this opening week of November. Temperature deficits of 7 degrees were posted at both Midway and O’Hare airports. The low of 32 degrees at O’Hare marks the city’s first freeze of the season, ending the 4th longest growing season since records began in 1871. The last official freeze was a 29-degree reading back on March 23rd. Much of the city proper has yet to experience a freezing temperature this fall. That is expected to change later this week. After a modest warm-up that may boost readings to near 50 degrees midweek, a reinforcing push of cold air is to sweep across the Great lakes. Though the core of coldest air will pass north of the area, temperatures are forecast to dip into the 20s across most of the metro area.