Frost dates for Harlan, IA
When the last spring frost and first fall frost usually come, and when to plant, from 30 years of NOAA weather records.
Last spring frost
April 27
typical year
Safe to plant
May 9
frost is over in 9 of 10 years
First fall frost
October 9
typical year
Growing season
165 days
frost-free, typical year
Frost watch this week
Tonight's and the next six nights' lows from the National Weather Service forecast for the station's location. Frost: 32°F or colder. Possible frost: 33–36°F, mostly in low spots on clear, still nights.
When to plant
Counted from this page's frost dates. Warm-season crops wait for the safe-to-plant date.
| Crop | Start indoors | Plant outside | Fall planting |
|---|---|---|---|
| Cool-season crops | |||
| Peas | – | Mar 30 – Apr 13 | – |
| Spinach | – | Mar 16 – Apr 6 | Aug 14 – 28 |
| Lettuce | – | Mar 30 – Apr 20 | Aug 14 – 28 |
| Radishes | – | Mar 30 – May 11 | Aug 28 – Sep 11 |
| Onions | – | Mar 30 – Apr 13 | – |
| Potatoes | – | Apr 6 – 20 | – |
| Carrots | – | Apr 6 – 27 | Jul 17 – 31 |
| Beets | – | Mar 30 – Apr 13 | Jul 31 – Aug 14 |
| Kale | Feb 16 – Mar 2 | Mar 30 – Apr 13 | Jul 31 – Aug 14 |
| Broccoli | Feb 16 – Mar 2 | Apr 13 – 27 | Jul 31 – Aug 14 |
| Cabbage | Feb 2 – 16 | Mar 30 – Apr 13 | Jul 31 – Aug 14 |
| Garlic | – | – | Aug 28 – Sep 18 |
| Warm-season crops | |||
| Tomatoes | Mar 14 – 28 | May 9 – 23 | – |
| Peppers | Mar 7 – 21 | May 16 – 30 | – |
| Cucumbers | – | May 9 – 30 | – |
| Zucchini | – | May 9 – Jun 6 | – |
| Pumpkins | – | May 9 – 30 | – |
| Green beans | – | May 9 – Jul 31 | – |
| Sweet corn | – | May 9 – Jun 6 | – |
| Basil | Apr 4 – 18 | May 16 – 23 | – |
Onions: from sets. Green beans: until 10 weeks before the first fall frost. Garlic: harvest next summer.
The year at a glance
Start indoors Plant outside Fall planting
The chance of frost, by date
| 1 year in 10 | Half of years | 9 years in 10 | |
|---|---|---|---|
| Spring frost after | May 9 | April 27 | April 12 |
| Fall frost before | September 24 | October 9 | October 22 |
Frost here means 32°F or colder. Read across: in 1 year in 10, spring frost carries on past the first date, which is why that date is the safe-to-plant date.
Hard freeze (28°F)
A hard freeze kills most garden plants, even hardy ones. The last one in spring usually comes around April 17 (April 30 in a late year), and the first one in fall around October 20.
Towns that use these dates
This is the nearest NOAA station with frost records for 11 towns.
Harlan, Avoca, Shelby, Earling, Irwin, Defiance, Panama, Portsmouth, Westphalia, Tennant, Kirkman
Where these dates come from
NOAA weather station HARLAN, IA US (USC00133632), 1991–2020 climate normals. It's the nearest station for 10 zip codes, all within 13 miles:
51446, 51447, 51521, 51527, 51530, 51537, 51562, 51565, 51570, 51578
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.