This post is part of a series that highlights sections of our forest management plan for Otter Point Woods. This particular post is little more data-dorky than normal, but I hope you find the links useful to look up information about your local climate since climate is important for plant growth—and pretty much everything else.

Average Temperature and Precipitation

Our regional climate is characterized by cold winters and summers that remain relatively cool. Average precipitation is about 28 inches, which is distributed throughout the year and heaviest during September and October (US Climate Data). Lake-effect snowfall from Lake Superior is common during the winter months, with the local airport weather station receiving 208 inches per year on average. Snowfall is highly variable across the region due to lake-effect snow; however, Otter Point Woods is outside of the strongest lake-effect zones and typically receives less snow than what is reported at the local weather station.

Average climate data from the Houghton County Airport in Hancock, MI, which is located approximately 20 miles north of the property (Source: US Climate Data):

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Average high (°F) 22 25 33 47 61 70 75 74 65 51 38 26
Average low (°F) 9 9 17 29 39 48 54 54 46 36 25 14
Average total precip (in) 2.6 1.4 1.6 1.9 2.5 2.6 2.5 2.4 3.5 3.0 2.1 1.9
Average snowfall (in) 69 31 19 8 1 0 0 0 0 5 22 53

Growing Season

The average growing season is 147 days, based on data from the nearest weather station. The average date of last freeze (32ºF) is May 10 and the average first frost day is October 5 (NCEI). These dates mean that there is a 50% chance of frost occurring after May 10 and also before October 5 in any given year. Taking a closer look at the data, there is a 90% probability that a freeze will not occur after May 24 or before September 19, and these dates provide a more conservative estimate for planting frost-sensitive plants. 

The plant hardiness zone for the area is 5a, which indicates an average winter minimum temperature of -15 to -20ºF (USDA ARS). (Click here to learn how to look up your growing season and hardiness zone.)

Climate Trends

The data presented above are generally based on the climate normals for the period 1981-2010, and so they only represent a 30-year portion of the climate record. I’ll be discussing climate change and its potential effects on the forest in more detail in future posts, but thought that it would be helpful to highlight some observed changes in temperature and precipitation in the meantime.

Plot of average annual temperature by year for 1985-2017.
Observed annual temperature for Michigan’s western Upper Peninsula (purple line). The trend (blue line) is that temperatures have increased more than 2.5ºF over the past century. Temperatures have warmed in all seasons, with the greatest warming in winter (data not shown). Data from NOAA’s Climate-at-a-Glance tool.

Observed annual precipitation for Michigan’s western Upper Peninsula (purple line). The trend (blue line) is that temperatures have increased more than 2 inches over the past century. Changes have been negligible in summer and winter, and the greatest increase has been in the fall (data not shown). Data from NOAA’s Climate-at-a-Glance tool.

It’s interesting to think about the amount of change that has occurred since the late 1800s. The start of the historical climate record is not long after the property was first surveyed by the General Land Office. At that time, everything was different: the trees (elm would have been much more abundant before Dutch elm disease), the land and waters (which had an entirely different arrangement), and even the climate.

I can’t help but wonder what this place will be like 100 and more years from now.

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