In order to further investigate this hypothesized connection, the present analysis considers aspects of the time series of 850 hPa temperature in a 20° x 20° box (25°N, 102.5°E to 45°N, 122.5°E) over 65 winter seasons (NDJFM, 1948/49 – 2012/13) using the NCEP-NCAR Reanalysis data. In particular, we constructed a time series of the daily perturbation 850 hPa temperature over the box by summing the daily departures at each grid point. Separate standard deviations for colder and warmer than normal days were calculated allowing identification of 2s cold and warm days. Composite differences in hemispheric circulation and 850 hPa temperature distribution between these extreme events are examined to reveal characteristic structures and synoptic evolutions associated with each. The tendency for extreme warm events to last longer than extreme cold events is investigated in the context of these circulation differences.