Frost dates for 37909Knoxville, TN
The average last spring frost in Knoxville is April 11 and the average first fall frost is October 28, giving a typical growing season of about 198 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 11
- Average first fall frost
- Oct 28
- Growing season
- 198 days
Safer after Apr 29 (1-in-10 risk)
Possible by Oct 13 (1-in-10 risk)
Last frost typically in 159 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Apr 9 · Apr 24 · May 10 | Oct 7 · Oct 19 · Nov 1 | 178 days | 100% |
| Frost / freeze (32°F) | Mar 26 · Apr 11 · Apr 29 | Oct 13 · Oct 28 · Nov 9 | 198 days | 100% |
| Hard freeze (28°F) | Mar 13 · Mar 31 · Apr 16 | Oct 24 · Nov 6 · Nov 20 | 221 days | 100% |
Planting calendar for Knoxville
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Mar 11 – May 17 |
| Tomatoes | Transplant outdoors | Apr 27 – Jul 8 |
| Peppers | Start seeds indoors | Mar 11 – Apr 11 |
| Peppers | Transplant outdoors | May 11 – Jun 11 |
| Eggplant | Start seeds indoors | Mar 28 – Apr 26 |
| Eggplant | Transplant outdoors | May 11 – Jun 11 |
| Cucumbers | Sow outdoors | May 11 – Jul 18 |
| Summer squash | Sow outdoors | Apr 27 – Jun 11 |
| Winter squash & pumpkins | Sow outdoors | May 11 – Jun 11 |
| Snap beans | Sow outdoors | Apr 27 – Aug 10 |
| Sweet corn | Sow outdoors | Apr 27 – Jul 8 |
| Watermelon & cantaloupe | Sow outdoors | May 11 – Jun 11 |
| Okra | Sow outdoors | May 4 – May 27 |
| Peas | Sow outdoors (spring) | Mar 11 – Apr 26 |
| Potatoes | Plant outdoors (spring) | Mar 11 – May 11 |
| Onions | Start seeds indoors (spring) | Jan 28 – Feb 24 |
| Onions | Transplant outdoors (spring) | Mar 28 – Apr 26 |
| Broccoli | Start seeds indoors (spring) | Feb 21 – Mar 27 |
| Broccoli | Transplant outdoors (spring) | Mar 28 – Apr 26 |
| Broccoli | Start seeds indoors (fall) | Jun 28 – Jul 8 |
| Broccoli | Transplant outdoors (fall) | Jul 28 – Aug 8 |
| Cabbage | Start seeds indoors (spring) | Feb 11 – Mar 11 |
| Cabbage | Transplant outdoors (spring) | Mar 11 – Apr 11 |
| Cabbage | Start seeds indoors (fall) | Jun 18 – Jul 18 |
| Cabbage | Transplant outdoors (fall) | Jul 18 – Aug 18 |
| Leaf lettuce | Sow outdoors (spring) | Mar 11 – May 27 |
| Leaf lettuce | Sow outdoors (fall) | Jul 18 – Sep 3 |
| Spinach | Sow outdoors (spring) | Mar 4 – Apr 17 |
| Spinach | Sow outdoors (fall) | Aug 4 – Sep 8 |
| Radishes | Sow outdoors (spring) | Mar 11 – May 1 |
| Radishes | Sow outdoors (fall) | Jul 18 – Sep 18 |
| Kale | Sow outdoors (spring) | Mar 28 – Apr 17 |
| Kale | Sow outdoors (fall) | Jul 11 – Aug 18 |
| Carrots | Sow outdoors (spring) | Apr 11 – May 27 |
| Carrots | Sow outdoors (fall) | Jun 18 – Aug 3 |
| Garlic | Plant outdoors (fall) | Oct 18 – Nov 18 |
Where these dates come from
ZIP code 37909 is matched to the NOAA station Knoxville Exp Stn, TN, 8 km away, at 830 ft elevation (115 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Knoxville Exp Stn, TN (used) | 830 ft | Apr 11 | Oct 28 |
| Knoxville Mcghee Tyson Ap, TN | 962 ft | Apr 1 | Nov 2 |
| Oak Ridge Asos, TN | 910 ft | Mar 31 | Nov 4 |
| Oak Ridge Atdd, TN | 905 ft | Apr 5 | Nov 1 |
Frost dates near Knoxville
- Knoxville, TN 37919 · last Apr 11, first Oct 28
- Powell, TN 37849 · last Apr 22, first Oct 25
- Louisville, TN 37777 · last Apr 1, first Nov 2
- Rockford, TN 37853 · last Apr 1, first Nov 2
- Alcoa, TN 37701 · last Apr 1, first Nov 2
- Heiskell, TN 37754 · last Apr 22, first Oct 25
- Maryville, TN 37804 · last Apr 11, first Oct 28
- Clinton, TN 37716 · last Mar 31, first Nov 4
Frequently asked questions
- When is the last frost in Knoxville, TN?
- For ZIP code 37909, the average last spring frost (32°F) is April 11, based on NOAA 1991-2020 climate normals for the Knoxville Exp Stn, TN weather station. There is a 1-in-10 chance of a frost after April 29.
- When is the first frost in Knoxville, TN?
- The average first fall frost (32°F) is October 28. There is a 1-in-10 chance of frost by October 13, so tender plants are at risk from that point on.
- How long is the growing season in 37909?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 198 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.