Frost dates for Mason City, 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 29
typical year
Safe to plant
May 9
frost is over in 9 of 10 years
First fall frost
October 7
typical year
Growing season
161 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 | – | Apr 1 – 15 | – |
| Spinach | – | Mar 18 – Apr 8 | Aug 12 – 26 |
| Lettuce | – | Apr 1 – 22 | Aug 12 – 26 |
| Radishes | – | Apr 1 – May 13 | Aug 26 – Sep 9 |
| Onions | – | Apr 1 – 15 | – |
| Potatoes | – | Apr 8 – 22 | – |
| Carrots | – | Apr 8 – 29 | Jul 15 – 29 |
| Beets | – | Apr 1 – 15 | Jul 29 – Aug 12 |
| Kale | Feb 18 – Mar 4 | Apr 1 – 15 | Jul 29 – Aug 12 |
| Broccoli | Feb 18 – Mar 4 | Apr 15 – 29 | Jul 29 – Aug 12 |
| Cabbage | Feb 4 – 18 | Apr 1 – 15 | Jul 29 – Aug 12 |
| Garlic | – | – | Aug 26 – Sep 16 |
| 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 29 | – |
| 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 29 | April 14 |
| Fall frost before | September 25 | October 7 | October 21 |
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 18 (April 30 in a late year), and the first one in fall around October 18.
Towns that use these dates
This is the nearest NOAA station with frost records for 6 towns.
Mason City, Nora Springs, Manly, Rockwell, Plymouth, Rock Falls
Where these dates come from
NOAA weather station MASON CITY, IA US (USC00135230), 1991–2020 climate normals. It's the nearest station for 6 zip codes, all within 11 miles:
50401, 50456, 50458, 50464, 50467, 50469
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.