If you haven’t yet done it, now is the time to remove the stems of herbaceous peonies, cut down stalks of tall perennials like Phlox and Monarda, and shear the leaves from Siberian iris. You’ll thank yourself in the springtime when you’re trying to figure out what is planted where. Is there a deadline for all of this activity? Not really. It’s really a matter of comfort—your comfort—while working outside. I’d rather wait until the insect population dies down and I don’t have to wear sunscreen. However, it’s up to the gardener to think about what her garden needs are to get through the winter.

Predicting the Weather?

Winter in the Midwest comes down to lowest historical temperature. An important resource for any gardener is the United States Department of Agriculture’s Plant Hardiness Zone Map. This tells you how cold it has gotten over the past several years. To pinpoint your USDA Hardiness Zone, go to the interactive zone map site, a handy tool to help estimate how cold it could get. Another handy guide that uses historical data to predict with some accuracy when it will get nippy is the Old Farmer’s Almanac. It gives the potential first frost or light freeze date.

I found a great article on the National Oceanic and Atmospheric Administration (NOAA) website that gives probability of first snowfall based on your location. It’s based on records between 1981 and 2010. NOAA also offers a site for true weather geeks that gives the U.S. Climate Normals in the 30 years between 1981 and 2010.

Meanwhile, NOAA offers the following definitions of frost and freeze:

• Frost: The deposition of ice crystals directly on the surface of exposed objects. In the right conditions (clear skies, winds less than 6 mph) frost can occur when observed air temperatures are several degrees above freezing.
• Freeze: When observed air temperatures fall to 32 F or lower.
• Killing Freeze: When observed air temperatures fall to 30 F or lower for at least two consecutive hours.
• Frost Advisory: Issued when frost is forecast to occur at 3 or more observation sites in either group 1, 2, or 3.
• Freeze Warning: Issued when a freeze is expected to occur at 3 or more observation sites in either group 1, 2, or 3.