Frost dates · USDA zone 5a
Frost dates for Waterloo, IA
Waterloo, IA sees its last 32 °F night of spring around April 27 and its first of fall around October 10 — a 165-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | Apr 11 | Oct 21 |
| Median — 1 year in 2 | Apr 27 | Oct 10 |
| 1 year in 10 | May 10 | Sep 26 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 165 days median, at least 146 in 9 years of 10, at least 184 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of Apr 16 and first of Oct 20.
Waterloo planting calendar, 2027
Every row runs from the median last frost (Apr 27) and median first frost (Oct 10) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Feb 2 | Mar 30 | Jul 18 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | Apr 27 | May 27 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Apr 13 | Apr 13 | May 28 | 45 from sow |
| Genovese BasilGenovese | Mar 30 | May 11 | Jul 10 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Mar 2 | May 4 | Jul 18 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Feb 16 | May 11 | Aug 14 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Mar 2 | May 4 | Jul 18 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Mar 2 | May 4 | Jul 23 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Mar 2 | May 4 | Jul 23 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Apr 13 | Apr 13 | Jun 22 | 70 from sow |
| TomatilloToma Verde | Mar 16 | May 4 | Jul 13 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Mar 16 | May 4 | Jul 18 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 16 | May 4 | Jul 23 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Waterloo grow?
Each sauce, scheduled for a Waterloo container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Waterloo frost questions
When is the last frost in Waterloo, IA?
The median last 32 °F freeze at WATERLOO MUNI AP, IA is April 27: half of years see a later one. One year in ten, a freeze still comes after May 10; nine years in ten, it comes after April 11. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Waterloo, IA?
The median first 32 °F freeze of fall is October 10. One year in ten it arrives before September 26; nine years in ten, before October 21.
How long is the growing season in Waterloo, IA?
165 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 146 days; one year in ten, at least 184 days.
What growing zone is Waterloo, IA?
USDA hardiness zone 5a, per the 2023 USDA Plant Hardiness Zone Map for ZIP 50702. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Waterloo, IA?
Start Roma VF (determinate paste) seeds indoors around Mar 16 and transplant around May 4, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for May 10. First ripe fruit lands around Jul 18.
When should I plant peppers in Waterloo, IA?
Sow jalapeño indoors on a heat mat around Mar 2; transplant no earlier than May 4, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Jul 18.
Nearby in Iowa
- Cedar Fallslast frost Apr 27
- Marionlast frost Apr 28
- Cedar Rapidslast frost Apr 28
- Iowa Citylast frost Apr 21
- Ameslast frost Apr 26
- Ankenylast frost Apr 23
All Iowa frost dates → · How frost-date math drives a sowing calendar →