St. Clair, Pennsylvania Weather
Cicadas claim the afternoon. Day 14 of summer. Read this microseason across nine climate regions →
St. Clair weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJul 4Rain32%0.11″97°72°—
- SundayJul 5Heavy Rain95%1.2″91°71°-6°
- MondayJul 6Thunderstorm95%0.32″74°63°-17°
- TuesdayJul 7Light Drizzle61%0.01″73°58°-1°
- WednesdayJul 8Mostly Clear20%—84°56°+11°
- ThursdayJul 9Light Drizzle37%—86°60°+2°
- FridayJul 10Light Drizzle37%—84°67°-2°
AQI 56 (Moderate), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 9.9 µg/m³ (AQI 52) with a 0.94 fine-to-coarse ratio and 6 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
Ozone × UV × Sky
Ozone at AQI 43 now. With UV 4.7 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 27 around 1 PM.
- Present
- AQI 43
- UV peak
- 4.7 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 27
PM × Wind × Precip
PM2.5 at 9.9 µg/m³ (AQI 52) with a 0.94 fine-to-coarse ratio and 6 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.94
- Wind
- light
- 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
- 10:59 PM
- Moonset
- 10:07 AM
- In sign
- ♓︎ Pisces
Cicadas claim the afternoon
St. Clair at a glance
- Today vs. normal: 12°F above the seasonal normal for this latitude
- Last frost: April 20 (climatological average for this latitude)
- Microseason: Jul 1–5
- Planting window: Harvest early potatoes. Begin drying onions on the surface.
16-Day Forecast — St. Clair
- Sat97°72°32%
- Sun91°71°95%
- Mon74°63°95%
- Tue73°58°61%
- Wed84°56°20%
- Thu86°60°37%
- Fri84°67°37%
- Sat82°69°27%
- Sun71°65°27%
- Mon70°63°18%
- Tue80°62°19%
- Wed83°63°30%
- Thu92°69°29%
- Fri92°71°36%
- Sat81°70°36%
- Sun87°65°39%
Forecast data from Open-Meteo (CC BY 4.0).
Right now in the garden
Peak growing season
As of July 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 — St. Clair
SPC has placed St. Clair in the Slight Risk category for severe thunderstorms today.
- TODAYSLGTSlight Risk
- TOMORROWMRGLMarginal 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.
ZIP codes in St. Clair
- 17970
- 17901