North Central Research Station

Extreme Cold Events

We used the National Climate Data Center's (NCDC) Summary of the Day daily minimum air temperature data for the 1950 to 1998 period, inclusive, to create a measure of extreme stress - the incidence of air temperatures less than or equal to -30°C.

Extreme cold events were mapped across USDA Forest Service Region 9 for each year, and as an average of the 1950-1998 period.

The frequency of extreme cold events during the 1950-1998 period was high in northern Minnesota (ie, 14+ days/year), but also was evident at a frequency of 6+ days/year in northern Wisconsin, Michigan, Vermont, New Hampshire, and Maine.  Minimum air temperatures below -30°C are unlikely to cause severe damage in these northern locations unless prolonged.

Extreme cold events that occur in more southern locations and in areas along the eastern coast of the New England States can be expected to cause more damage.  In these locations, forest hardening is typically less, whereas native trees in northern continental locations typically "frost harden" to -45°C.

Maps indicate that the southern limit of -30°C events from 1990 to 1998 varied annually by as much as 400 km.  This suggests that southern and coastal areas could experience damage from these types of events periodically.

Maps of extreme cold events for each year can be viewed below:

Publications can be obtained from your local library, the appropriate journal, or the authors, if supplies remain.

• Monitoring the effects of extreme climate disturbances on forest health in the Northeast US  Auclair A, Heilman W, Busalacchi P. 2003. American Meteorological Society. 6(12):146-151.

For more information:

• Warren E Heilman  Project Leader, Research Meteorologist