Postville, Iowa Weather
Prairie lightning bugs rise. Day 77 of spring. Read this microseason across nine climate regions →
Postville weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Rain78%0.25″85°56°—
- FridayJun 5Thunderstorm74%0.17″78°66°-7°
- SaturdayJun 6Light Rain31%0.07″82°65°+4°
- SundayJun 7Light Showers47%0.03″75°65°-7°
- MondayJun 8Showers72%0.18″74°65°-1°
- TuesdayJun 9Showers47%0.01″76°67°+2°
- WednesdayJun 10Thunderstorm19%—86°67°+10°
Ozone at AQI 61 — peak already passed at 1 PM under clear skies. AQI up 13 over the last 6 hours (gradual rise). Levels should ease through evening.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 61 — peak already passed at 1 PM under clear skies. Levels should ease through evening.
- Present
- AQI 61
- UV peak
- 1.9 at earlier today
- Sky at peak
- clear
- Projected peak
- AQI 61
PM × Wind × Precip
PM scrubbed by 3 hours of recent rain — PM2.5 down to 8.6 µg/m³, PM10 to 10.5 µg/m³.
- PM2.5/PM10
- 0.82
- Wind
- breezy
- Recent rain
- 3h in last 6h
- Pattern
- washed out
Trends
Seven days of AQI and PM2.5.
Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 4:46 AM
- Moonset
- 1:59 PM
- In sign
- ♒︎ Aquarius
Prairie lightning bugs rise
Postville at a glance
- Today vs. normal: 11°F above the seasonal normal for this latitude
- Last frost: May 5 (climatological average for this latitude)
- Microseason: Jun 1–5
- Planting window: Harvest spring lettuce before it bolts. Sow heat-tolerant greens.
Right now in the garden
Peak growing season
As of June 4, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.
SPC Convective Outlook
Storm Prediction Center — Postville
SPC has placed Postville in the Slight Risk category for severe thunderstorms tomorrow.
- TODAYMRGLMarginal Risk
- TOMORROWSLGTSlight Risk
- DAY 3TSTMGeneral Thunderstorms
Scattered severe storms possible. A few tornadoes, hail, and damaging wind gusts possible.
Source: NOAA / NWS Storm Prediction Center categorical convective outlook. Outlooks are re-issued multiple times per day; this page reflects the most recent SPC polygons covering the city’s coordinates.
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | — | — |
| February | — | — |
| March | — | — |
| April | — | — |
| May | lettuce, peas, spinach, radishes | lettuce, peas, radishes |
| June | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | tomatoes, peppers, beans, squash | tomatoes, beans, summer squash |
| August | tomatoes, peppers, beans, squash, fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| September | fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| October | — | winter squash, tomatoes (last) |
| November | — | — |
| December | — | — |
A year in weather
Postville's warmest month is July (~72°F mean) and its coldest is January (~17°F). Rainfall peaks in June (5.9 inches) and bottoms out in January (1.1 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 17° | 1.1″ | 4 |
| February | 20° | 1.2″ | 4 |
| March | 33° | 2.1″ | 5 |
| April | 46° | 4.1″ | 7 |
| May | 58° | 5.0″ | 9 |
| June | 68° | 5.9″ | 9 |
| July | 72° | 4.5″ | 7 |
| August | 70° | 4.4″ | 7 |
| September | 62° | 4.0″ | 7 |
| October | 49° | 3.0″ | 5 |
| November | 35° | 2.1″ | 4 |
| December | 23° | 1.6″ | 4 |
Regional context
Postville's climate, per the NOAA NCEI 1991-2020 normals from the nearest reporting station, runs cold-winter and warm-summer. January means hover near 17°F while July climbs to 72°F — a 55°F seasonal swing typical of northern-tier latitudes. Annual precipitation totals about 38.9 inches spread across roughly 71 days with measurable rain or snow.
Precipitation runs summer-dominant here: June averages 5.9 inches across 9.0 days with measurable rain, driven mostly by warm-season storms and thunderstorm activity, while January drops to just 1.1 inches across 3.6 rainy days under drier cool-season air. The warm-season-wet rhythm lines Postville up with places like Castalia, IA, Luana, IA and Clermont, IA, where the May-September stretch delivers the bulk of the year's precipitation.
The frost-sensitive growing window opens around late-May, when overnight lows reliably clear freezing for cool-season crops like kale, peas, spinach, and parsnips. Heat-loving transplants like tomatoes, peppers, and squash generally hold off for another 10-14 days to clear the last spring frost risk window. The window closes around early-October, when overnight lows resume dipping below freezing and frost-tender plants need protection or harvest. These are 30-year central tendencies; year-to-year frost dates can move by up to two weeks. Local features matter: a south-facing slope inside Postville typically runs 3-5 days ahead of the regional last-frost date, while a low-lying lot along a creek or drainage can lag the same date by a week or more on calm clear nights.
Similar climates: Castalia, IA, Luana, IA, Clermont, IA, Monona, IA, Elgin, IA.
Frequently asked
- When does it freeze in Postville?
- Postville's last spring frost typically falls around mid-May, and the first fall frost arrives around mid-October.
- What is the rainy season in Postville?
- June is the wettest month with about 5.9 inches of rain on average; the city receives roughly 39 inches annually.
- What is the warmest month in Postville?
- July is typically warmest, averaging about 72°F.
- What is the coldest month in Postville?
- January is typically coldest, averaging about 17°F.
- When can I start a vegetable garden in Postville?
- Cool-season crops (peas, lettuce) can be sown around the last spring frost (mid-May); warm-season crops (tomatoes, peppers) wait until 1–2 weeks after.
- How many rainy days does Postville get?
- Postville averages about 71 rainy days per year.
- What hardiness zone is Postville?
- Postville's USDA hardiness zone is determined by its lowest average winter temperature; check the USDA's online lookup with the city ZIP for the current zone designation.
Climate
Postville, Iowa sits in a warm-summer humid continental climate zone. January means hover near 17°F while July averages 72°F — a 55°F seasonal swing.
Across the year, Postville receives about 39 inches of precipitation spread over roughly 71 rainy days.
The rhythm of the year is set by latitude (43.1°N), proximity to large water bodies, and elevation — all of which shape what grows here, when frost is likely, and what the weather story looks like day to day.