As part of my commitment to providing accurate and trustworthy information, this page contains the raw data used to create my planting calendars. I compiled the frost dates below from trusted sources for several populous cities within each USDA Zone. From this data, I establish the two key baselines used throughout this site: the Aggressive Baseline (calculated from the average frost date) and the Safe Baseline (determined by the most conservative date).
A Quick Guide to the Baselines Below
- Aggressive Spring Baseline: The calculated average of the last spring frost dates.
- Safe Spring Baseline: The single latest last frost date from the data.
- Aggressive Fall Baseline: The calculated average of the first fall frost dates.
- Safe Fall Baseline: The single earliest first fall frost date from the data.
Wait, why is the “Aggressive” fall date later than the “Safe” one?
Good catch! This is intentional. The “Aggressive” fall strategy aims to maximize the growing season by pushing the harvest as late as possible. This requires planting later in the summer, which carries a higher risk of an unexpected early frost.
USDA Zone 4 Frost Date Data
| City (Zip Code) | Last Spring Frost Data | First Fall Frost Data |
| 55901,Rochester, Minnesota | May 5 | Oct 1 |
| 54701,Eau Claire, Wisconsin | Apr 30 | Oct 7 |
| 58102, Fargo, North Dakota | May 15 | Sep 25 |
| 58501, Bismarck, North Dakota | May 14 | Sep 25 |
Based on the data above, the four key baseline dates for the Zone 4 planting calendars are as follows:
- Aggressive Spring Planting Baseline:May 9
- Safe Spring Planting Baseline:May 15
- Aggressive Fall Planting Baseline:Sep 30
- Safe Fall Planting Baseline:Sep 25
USDA Zone 5 Frost Date Data
| City (Zip Code) | Last Spring Frost Data | First Fall Frost Data |
| 55401,Minneapolis, Minnesota | Apr 30 | Oct 10 |
| 53701,Madison, Wisconsin | May 7 | Oct 3 |
| 55101, Saint Paul, Minnesota | Apr 30 | Oct 10 |
| 50303, Des Moines, lowa | Apr 24 | Oct 14 |
Based on the data above, the four key baseline dates for the Zone 5 planting calendars are as follows:
- Aggressive Spring Planting Baseline:Apr 30
- Safe Spring Planting Baseline:May 7
- Aggressive Fall Planting Baseline:Oct 9
- Safe Fall Planting Baseline:Oct 3
USDA Zone 6 Frost Date Data
| City (Zip Code) | Last Spring Frost Data | First Fall Frost Data |
| 60601,Chicago, lllinois | Apr 17 | Nov 1 |
| 43201,Columbus, Ohio | Apr 27 | Oct 20 |
| 46201,Indianapolis, Indiana | Apr 26 | Oct 16 |
| 80201,Denver, Colorado | May 8 | Oct 2 |
Based on the data above, the four key baseline dates for the Zone 6 planting calendars are as follows:
- Aggressive Spring Planting Baseline:Apr 27
- Safe Spring Planting Baseline:May 8
- Aggressive Fall Planting Baseline:Oct 18
- Safe Fall Planting Baseline:Oct 2
USDA Zone 7 Frost Date Data
| City (Zip Code) | Last Spring Frost Data | First Fall Frost Data |
| 10001, New York, New York | Apr 3 | Nov 14 |
| 19101, Philadelphia, Pennsylvania | Apr 4 | Nov 11 |
| 73101,Oklahoma City, Oklahoma | Apr 8 | Oct 30 |
| 37210,Nashville,Tennessee | Apr 7 | Oct 25 |
Based on the data above, the four key baseline dates for the Zone 7 planting calendars are as follows:
- Aggressive Spring Planting Baseline:Apr 6
- Safe Spring Planting Baseline:Apr 8
- Aggressive Fall Planting Baseline:Nov 5
- Safe Fall Planting Baseline:Oct 25
USDA Zone 8 Frost Date Data
| City (Zip Code) | Last Spring Frost Data | First Fall Frost Data |
| 75201,Dallas, Texas | Mar 9 | Nov 20 |
| 76101,Fort Worth, Texas | Mar 12 | Nov 14 |
| 28201,Charlotte, North Carolina | Apr 5 | Oct 30 |
| 20001,Washington, District of Columbia | Apr 3 | Nov 2 |
Based on the data above, the four key baseline dates for the Zone 8 planting calendars are as follows:
- Aggressive Spring Planting Baseline:Mar 23
- Safe Spring Planting Baseline:Apr 5
- Aggressive Fall Planting Baseline:Nov 9
- Safe Fall Planting Baseline:Oct 30
USDA Zone 9 Frost Date Data
| City (Zip Code) | Last Spring Frost Data | First Fall Frost Data |
| 77001,Houston, Texas | Feb 18 | Dec 8 |
| 78201,San Antonio, Texas | Mar 5 | Nov 18 |
| 32201,Jacksonville, Florida | Feb 15 | Dec 24 |
| 78701,Austin, Texas | Mar 18 | Nov 10 |
Based on the data above, the four key baseline dates for the Zone 9 planting calendars are as follows:
- Aggressive Spring Planting Baseline:Feb 28
- Safe Spring Planting Baseline:Mar 18
- Aggressive Fall Planting Baseline:Nov 30
- Safe Fall Planting Baseline:Nov 10
By making this data publicly available, I hope to earn your trust and empower you with the knowledge that your planting calendars are based on sound, verifiable science. To understand how I use these dates to create your custom calendars, please visit the “My Methodology” page.