Johnston, Iowa Weather
Cicadas claim the afternoon. Day 15 of summer. Read this microseason across nine climate regions →
Johnston weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJul 4Heavy Rain77%0.78″85°67°—
- SundayJul 5Overcast11%—84°68°-1°
- MondayJul 6Clear——86°67°+2°
- TuesdayJul 7Overcast——87°66°+1°
- WednesdayJul 8T-storm w/ Hail32%—89°67°+2°
- ThursdayJul 9Heavy Drizzle35%0.01″78°65°-11°
- FridayJul 10Overcast17%—83°65°+5°
AQI 46 (Good), driven by PM2.5. AQI up 12 over the last 6 hours (gradual rise). PM2.5 at 6.8 µg/m³ (AQI 38) with a 0.92 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in calm air, not road dust.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
PM × Wind × Precip
PM2.5 at 6.8 µg/m³ (AQI 38) with a 0.92 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.92
- Wind
- calm
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
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).
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
- Moonrise
- 11:35 PM
- Moonset
- 11:27 AM
- In sign
- ♓︎ Pisces
Cicadas claim the afternoon
Johnston at a glance
- Today vs. normal: 7°F above the seasonal normal for this latitude
- Last frost: April 26 (climatological average for this latitude)
- Microseason: Jul 1–5
- Planting window: Harvest early potatoes. Begin drying onions on the surface.
ZIP code: 50131
16-Day Forecast — Johnston
- Sat85°67°77%
- Sun84°68°11%
- Mon86°67°1%
- Tue87°66°1%
- Wed89°67°32%
- Thu78°65°35%
- Fri83°65°17%
- Sat78°65°8%
- Sun79°61°8%
- Mon85°61°5%
- Tue90°70°6%
- Wed88°69°8%
- Thu92°70°19%
- Fri95°73°14%
- Sat96°77°19%
- Sun86°65°13%
Forecast data from Open-Meteo (CC BY 4.0).
Right now in the garden
Peak growing season
As of July 5, 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 — Johnston
SPC includes Johnston in the general thunderstorm area today — no severe risk, but storms are possible.
- TODAYTSTMGeneral Thunderstorms
- TOMORROWTSTMGeneral Thunderstorms
- DAY 3NONENo severe risk
Thunderstorms possible. Not severe, but capable of producing lightning and brief heavy rain.
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.
ZIP codes in Johnston
- 50131