USDA Hardiness Zone 7b
Frost Dates for 37308 — Birchwood, Tennessee
NOAA 1991–2020 normals from Dayton 2SE, TN (822 ft), 8 miles north.
Updated
In Birchwood, the last spring frost (32°F) is around April 4 in half of years and has passed by April 22 in nine years out of ten. The first fall frost comes around October 31, as early as October 19 one year in ten, leaving a typical freeze-free season of 208 days (NOAA, Dayton 2SE, TN).
- Last spring frost
- April 4
- First fall frost
- October 31
- Growing season
- 208 days
- Hardiness zone
- 7b
50% probability
50% probability
freeze-free, 50%
5 to 10°F (-15.0 to -12.2°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 40%
- Snow per year
- 1.1"
median, 1991–2020
median, 1991–2020
12 of 30 observed
NOAA normal
Frost risk by date in Birchwood
Half of springs at Dayton 2SE, TN see their last 32°F night by April 4; only one in ten is past it by March 18, and one in ten still has one after April 22. Planting tender crops after April 11 leaves a 30% risk of a frost on them, after April 16 20%, and after April 22 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 67% of the 144 Tennessee stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 31 in half of years, as early as October 19 one year in ten, and holds off past November 12 one year in ten. A hard freeze of 28°F follows 10 days later, around November 10; in spring the one-in-ten date for 28°F is April 9, 13 days before the 32°F one. The freeze-free season lasts 208 days in a typical year, longer than at 61% of the 144 Tennessee stations; it reaches 229 days one year in ten and falls short of 187 one year in ten. On average 72 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 14 days longer, to about April 18, and return around October 22. Severe cold of 16°F or below comes in 95% of winters, usually between December 31 and February 7.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 31 | Apr 6 | Apr 10 | Apr 14 | Apr 18 | Apr 21 | Apr 24 | Apr 29 | May 3 |
| 32°F | Mar 18 | Mar 25 | Mar 30 | Apr 1 | Apr 4 | Apr 7 | Apr 11 | Apr 16 | Apr 22 |
| 28°F | Mar 6 | Mar 14 | Mar 17 | Mar 22 | Mar 26 | Mar 29 | Apr 1 | Apr 4 | Apr 9 |
| 24°F | Feb 19 | Feb 27 | Mar 4 | Mar 8 | Mar 12 | Mar 16 | Mar 20 | Mar 26 | Mar 31 |
| 20°F | Jan 30 | Feb 6 | Feb 14 | Feb 20 | Feb 26 | Mar 2 | Mar 7 | Mar 13 | Mar 20 |
| 16°F95% of yrs | Jan 9 | Jan 20 | Jan 27 | Feb 1 | Feb 7 | Feb 13 | Feb 20 | Feb 28 | Mar 6 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 9 | Oct 14 | Oct 17 | Oct 20 | Oct 22 | Oct 24 | Oct 27 | Oct 30 | Nov 2 |
| 32°F | Oct 19 | Oct 22 | Oct 26 | Oct 28 | Oct 31 | Nov 1 | Nov 4 | Nov 8 | Nov 12 |
| 28°F | Oct 28 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 13 | Nov 16 | Nov 21 | Nov 29 |
| 24°F | Nov 6 | Nov 12 | Nov 15 | Nov 20 | Nov 24 | Nov 29 | Dec 2 | Dec 7 | Dec 16 |
| 20°F | Nov 16 | Nov 24 | Nov 30 | Dec 4 | Dec 8 | Dec 15 | Dec 23 | Dec 30 | Jan 7 |
| 16°F95% of yrs | Dec 1 | Dec 9 | Dec 19 | Dec 25 | Dec 31 | Jan 3 | Jan 7 | Jan 13 | Jan 22 |
Freeze probabilities 1991–2020 at Dayton 2SE, TN, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 37308 →Compare Birchwood with another place →
Weather by month in Birchwood
July is the warmest month at Dayton 2SE, TN, averaging 88°F by day and 67°F at night; January is the coldest at 47°F and 28°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 62% of years.
Warmth for growing adds up to 4,363 growing degree days a year (base 50°F), fewer than at 60% of the 144 Tennessee stations. 38% of them (1,653) have built up by the end of June, and July adds the most, 846. Precipitation totals 58.7 inches a year, most in December (6.0") and least in October (3.6"); May to September bring 40% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 47 | 28 | 5.2 | 100% | 20 | 17 |
| Feb | 52 | 31 | 5.1 | 100% | 15 | 24 |
| Mar | 61 | 38 | 5.3 | 99% | 9 | 103 |
| Apr | 71 | 46 | 5.4 | 62% | 1 | 275 |
| May | 78 | 55 | 4.8 | 2% | 0 | 513 |
| Jun | 85 | 63 | 4.5 | 0% | 0 | 721 |
| Jul | 88 | 67 | 5.3 | 0% | 0 | 846 |
| Aug | 87 | 66 | 3.9 | 0% | 0 | 826 |
| Sep | 82 | 60 | 4.8 | 0% | 0 | 626 |
| Oct | 71 | 48 | 3.6 | 52% | 1 | 308 |
| Nov | 59 | 37 | 4.8 | 99% | 9 | 79 |
| Dec | 50 | 31 | 6.0 | 100% | 18 | 26 |
Monthly normals 1991–2020 at Dayton 2SE, TN (822 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Cleveland Fltr Plt, TN, 15 miles southeast of Birchwood, has a last frost 2 days later (April 6), a first frost 1 day earlier (October 30), a season 2 days shorter.
When it snows in Birchwood, Tennessee
Measurable snow is rare here: only 12 of 30 winters from 1991 to 2020 recorded 0.1 inch or more at Cleveland Fltr Plt, TN, 14.8 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 37308
| When | What to do |
|---|---|
| January 24 – February 7 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 7 – February 21 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 7 – March 21 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 4 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 8 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 17 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 31 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 37308 is 8 miles from Dayton 2SE, TN, which stands at 822 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 37321 (Dayton). The 2023 USDA Plant Hardiness Zone Map lists ZIP 37308 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Tennessee →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.