Vermont Winter Soil Temperatures
Dr. Leonard Perry, Extension Professor, University of Vermont
For over 16 years I have monitored soil temperatures in field perennial beds,
at various locations, depths, and combinations of mulch in USDA zone 4 in Milton
VT, in a loam soil. The following were taken at a depth of 2 inches similar to
many perennial crowns, with no mulch except for natural snow cover. Some years,
or specific data a certain year, were not available for various reasons (or not
below 32ºF), yet sufficient results over this period should provide useful
information. Data was collected for the first time temperatures dropped below (1st<40ºF),
or rose above (1st>40ºF) 40ºF, and when they stayed below this
(<40ºF) or above this (>40ºF). For many perennials 40ºF this is roughly
where roots are reported to stop growing.
| Year | 1st<40ºF | <40ºF | <32ºF | 1st>40ºF | >40ºF |
| 06-07 | 11/20 | 1/7 | -- | 3/25 | 4/18 |
| 05-06 | 11/9 | 12/2 | 2/11 | 3/14 | 4/11 |
| 04-05 | 11/6 | 11/26 | 12/30 | 3/24 | 4/16 |
| 03-04 | 11/8 | 12/1 | 1/9 | 3/26 | 4/16 |
| 02-03 | -- | 11/23 | 1/5 | 3/18 | 4/26 |
| 01-02 | 11/10 | 12/8 | -- | 3/9 | 4/13 |
| 00-01 | 11/8 | 11/17 | 12/6 | -- | 4/29 |
| 99-00 | 11/1 | 12/10 | 12/26 | 3/23 | 4/1 |
| 98-99 | 11/4 | 12/22 | -- | -- | -- |
| 97-98 | 11/4 | 11/13 | 1/3 | 3/17 | 4/13 |
| 96-97 | -- | 11/17 | 1/1 | -- | -- |
| 95-96 | 10/26 | 12/2 | 12/30 | 3/15 | 4/22 |
| 94-95 | -- | 1/22 | -- | 3/8 | -- |
| 93-94 | 10/14 | 12/1 | 12/16 | 3/30 | -- |
| 90-91 | 10/27 | 11/25 | 12/31 | 3/16 | 4/22 |
| 89-90 | 11/5 | 11/17 | 11/29 | 3/11 | 4/19 |
| Average | 11/3 | 12/4 | 12/29 | 3/18 | 4/17 |
| Range | 10/14-11/10 | 11/13-1/22 | 11/29-2/11 | 3/8-3/30 | 4/1-4/29 |