Plan your vegetable garden in Union County
All the statistical weather information you need to prepare a bulletproof plan for your garden in Union County, Iowa
Temperature range in Union County
Union County has temperatures ranging from -20°F to 91°F, with approximately 172 frost free days.
Union County has 145 days with average temperature range from 50°F to 90°F that are suitable for growing warm season vegetables and 169 days with average temperature range from 40°F to 80°F that are suitable for growing cool season vegetables
Union County, Iowa air temperature chart based on weather statistics from 2019 to 2023
| Total frost free days (after last frost and before first frost) | 172 |
| Total days suitable to grow warm season vegetables | 145 |
| Total days suitable to grow cool season vegetables | 169 |
| Day with highest recorded temperature in past 4 years | June 17: 91°F |
| Day with lowest recorded temperature in past 4 years | January 30: -20°F |
| First expected frost date | October 17 |
| Last expected frost date | April 28 |
Notable temperature facts for gardening in Union County, Iowa
Warm season vegetables you can grow in Union County
Days suitable for growing warm season vegetables in Union County, Iowa
Warm season vegetables can be planted in Union County, Iowa after May 21 when air temperatures are consistently above 50°F (10°C) and soil temperature is above 50°F (10°C)
Good temperature range for warm season vegetables is between 50°F and 90°F. With warm season vegetables it is important to wait until all conditions are optimal, because sudden temperature drop can stun new vegetable growth, this way delaying overall harvest.
Warm season vegetables that can be planted directly into soil in Union County
Cool season vegetables you can grow in Union County
Days suitable for growing cool season vegetables in Union County, Iowa
Cool season vegetables can be planted in Union County, Iowa after April 27 when average air temperature is consistently above 40°F (4°C) and soil temperature is above 45°F (7°C)
Good temperature range for cool season vegetables is between 40°F and 80°F. With cool season vegetables it is important to avoid high air temperatures because exposure to high temperatures is most likely to stun growth, cause bitterness and encourage premature bolting in some plants. Plan your cool vegetable planting so they are harvested before hot weather stretch, provide them with additional shading.
Cool season vegetables that can be planted directly into soil in Union County
Table with days suitable to grow vegetables in Union County, Iowa
Tolerable temperature range for cool season vegetables: 40°F to 80°F
Tolerable temperature range for warm season vegetables: 50°F to 90°F
| Week | Average temperature | Possible min and max temperature | Suitable for cool season vegetables | Suitable for warm season vegetables | |
|---|---|---|---|---|---|
| 1 | January 01 - January 03 | 18°F to 34°F | -6°F to 46°F | ||
| 2 | January 04 - January 10 | 24°F to 37°F | 0°F to 53°F | ||
| 3 | January 11 - January 17 | 24°F to 36°F | 2°F to 49°F | ||
| 4 | January 18 - January 24 | 15°F to 29°F | -11°F to 44°F | ||
| 5 | January 25 - January 31 | 13°F to 28°F | -20°F to 47°F | ||
| 6 | February 01 - February 07 | 18°F to 35°F | -9°F to 55°F | ||
| 7 | February 08 - February 14 | 16°F to 30°F | -8°F to 52°F | ||
| 8 | February 15 - February 21 | 16°F to 34°F | -16°F to 57°F | ||
| 9 | February 22 - February 28 | 21°F to 38°F | -3°F to 57°F | ||
| 10 | March 01 - March 07 | 26°F to 46°F | -5°F to 64°F | ||
| 11 | March 08 - March 14 | 31°F to 46°F | 11°F to 67°F | ||
| 12 | March 15 - March 21 | 32°F to 50°F | 12°F to 64°F | ||
| 13 | March 22 - March 28 | 36°F to 50°F | 22°F to 63°F | ||
| 14 | March 29 - April 04 | 36°F to 55°F | 22°F to 74°F | ||
| 15 | April 05 - April 11 | 41°F to 59°F | 24°F to 73°F | TRUE | |
| 16 | April 12 - April 18 | 37°F to 54°F | 23°F to 72°F | ||
| 17 | April 19 - April 25 | 41°F to 58°F | 25°F to 73°F | TRUE | |
| 18 | April 26 - May 02 | 45°F to 62°F | 29°F to 76°F | TRUE | |
| 19 | May 03 - May 09 | 47°F to 63°F | 37°F to 82°F | TRUE | |
| 20 | May 10 - May 16 | 50°F to 65°F | 35°F to 81°F | TRUE | |
| 21 | May 17 - May 23 | 52°F to 66°F | 39°F to 78°F | TRUE | TRUE |
| 22 | May 24 - May 30 | 55°F to 70°F | 40°F to 80°F | TRUE | TRUE |
| 23 | May 31 - June 06 | 57°F to 74°F | 48°F to 81°F | TRUE | TRUE |
| 24 | June 07 - June 13 | 59°F to 76°F | 47°F to 88°F | TRUE | TRUE |
| 25 | June 14 - June 20 | 62°F to 79°F | 55°F to 91°F | TRUE | TRUE |
| 26 | June 21 - June 27 | 62°F to 77°F | 51°F to 87°F | TRUE | TRUE |
| 27 | June 28 - July 04 | 64°F to 79°F | 58°F to 88°F | TRUE | TRUE |
| 28 | July 05 - July 11 | 63°F to 77°F | 54°F to 89°F | TRUE | TRUE |
| 29 | July 12 - July 18 | 63°F to 79°F | 56°F to 86°F | TRUE | TRUE |
| 30 | July 19 - July 25 | 64°F to 80°F | 55°F to 88°F | TRUE | TRUE |
| 31 | July 26 - August 01 | 64°F to 79°F | 56°F to 88°F | TRUE | TRUE |
| 32 | August 02 - August 08 | 63°F to 77°F | 51°F to 90°F | TRUE | TRUE |
| 33 | August 09 - August 15 | 63°F to 78°F | 54°F to 85°F | TRUE | TRUE |
| 34 | August 16 - August 22 | 61°F to 77°F | 54°F to 85°F | TRUE | TRUE |
| 35 | August 23 - August 29 | 65°F to 79°F | 54°F to 88°F | TRUE | TRUE |
| 36 | August 30 - September 05 | 60°F to 76°F | 52°F to 84°F | TRUE | TRUE |
| 37 | September 06 - September 12 | 58°F to 73°F | 45°F to 84°F | TRUE | TRUE |
| 38 | September 13 - September 19 | 58°F to 74°F | 46°F to 81°F | TRUE | TRUE |
| 39 | September 20 - September 26 | 56°F to 71°F | 45°F to 86°F | TRUE | TRUE |
| 40 | September 27 - October 03 | 55°F to 71°F | 39°F to 82°F | TRUE | TRUE |
| 41 | October 04 - October 10 | 49°F to 65°F | 36°F to 76°F | TRUE | |
| 42 | October 11 - October 17 | 45°F to 60°F | 32°F to 74°F | TRUE | |
| 43 | October 18 - October 24 | 44°F to 59°F | 26°F to 76°F | TRUE | |
| 44 | October 25 - October 31 | 36°F to 49°F | 23°F to 66°F | ||
| 45 | November 01 - November 07 | 38°F to 54°F | 20°F to 69°F | ||
| 46 | November 08 - November 14 | 35°F to 49°F | 9°F to 66°F | ||
| 47 | November 15 - November 21 | 34°F to 49°F | 17°F to 63°F | ||
| 48 | November 22 - November 28 | 30°F to 44°F | 19°F to 54°F | ||
| 49 | November 29 - December 05 | 30°F to 45°F | 18°F to 56°F | ||
| 50 | December 06 - December 12 | 28°F to 42°F | 18°F to 56°F | ||
| 51 | December 13 - December 19 | 24°F to 38°F | 11°F to 65°F | ||
| 52 | December 20 - December 26 | 25°F to 40°F | -8°F to 55°F | ||
| 53 | December 27 - December 31 | 26°F to 40°F | 0°F to 56°F |
Days suitable to grow vegetables in Union County, Iowa
All data is provided “as is” without warranty or any representation of accuracy, timeliness or completeness.
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Average daily temperatures were calculated using
