Johnstown, Colorado Weather
Pikas hayfeeding in granite peaks. Day 76 of spring. Read this microseason across nine climate regions →
Johnstown weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Overcast34%—85°51°—
- ThursdayJun 4Overcast——91°51°+6°
- FridayJun 5Clear——89°57°-2°
- SaturdayJun 6Light Drizzle——96°59°+7°
- SundayJun 7Overcast15%—95°59°-1°
- MondayJun 8Light Drizzle36%0.01″90°60°-5°
- TuesdayJun 9Overcast31%—97°55°+7°
Ozone at AQI 73 — peak already passed at 1 PM under clear skies. AQI flat over the last 6 hours (within ±3 points). 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 73 — peak already passed at 1 PM under clear skies. Levels should ease through evening.
- Present
- AQI 73
- UV peak
- 3.6 at earlier today
- Sky at peak
- clear
- Projected peak
- AQI 73
PM × Wind × Precip
PM2.5/PM10 ratio 0.58 with 12 mph wind — characteristic of long-range haze transport rather than a local source.
- PM2.5/PM10
- 0.58
- Wind
- breezy
- Recent rain
- 0h in last 6h
- Pattern
- transport
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).
The higher the clouds, the finer the weather.
- Moonrise
- 4:54 AM
- Moonset
- 2:00 PM
- In sign
- ♑︎ Capricorn
Pikas hayfeeding in granite peaks
Johnstown at a glance
- Today vs. normal: 7°F above the seasonal normal for this latitude
- Last frost: April 18 (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
Warm-season window is open
As of June 3, the last spring frost has passed for most years. Transplant tomatoes, peppers, eggplants, basil, and cucurbits (cucumbers, squash, melons) now. Direct-sow beans and corn into warm soil.
SPC Convective Outlook
Storm Prediction Center — Johnstown
SPC has placed Johnstown in the Marginal Risk category for severe thunderstorms today.
- TODAYMRGLMarginal Risk
- TOMORROWTSTMGeneral Thunderstorms
- DAY 3NONENo severe risk
Isolated severe storms possible. Limited threat for hail or damaging wind.
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.