Heidelberg, Pennsylvania Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
Heidelberg weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Clear——82°48°—
- ThursdayJun 4Overcast——86°56°+4°
- FridayJun 5Overcast——87°60°+1°
- SaturdayJun 6Light Showers83%—85°62°-2°
- SundayJun 7Drizzle83%—82°64°-3°
- MondayJun 8Overcast——85°61°+3°
- TuesdayJun 9Partly Cloudy11%—87°64°+2°
PM2.5 at 33.3 µg/m³ (AQI 96) with a 0.99 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in calm air, not road dust. AQI down 19 over the last 6 hours — air quality is improving sharply.
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 33.3 µg/m³ (AQI 96) with a 0.99 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.99
- Wind
- calm
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
NO₂ × Time of day
NO₂ at AQI 30 during overnight — within the expected overnight baseline, no source signature.
- Present
- AQI 30
- Phase
- overnight calm
- Pattern
- traffic typical
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
- 3:50 AM
- Moonset
- 1:19 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
Heidelberg at a glance
- Today vs. normal: 8°F below 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
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.
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | — | — |
| February | — | — |
| March | — | — |
| April | lettuce, peas, spinach, radishes | — |
| May | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| June | tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | tomatoes, peppers, beans, squash | tomatoes, beans, summer squash |
| August | — | tomatoes, beans, summer squash |
| September | fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| October | fall brassicas, garlic (overwinter), carrots | winter squash, tomatoes (last) |
| November | — | — |
| December | — | — |
A year in weather
Heidelberg's warmest month is July (~74°F mean) and its coldest is January (~30°F). Rainfall peaks in June (4.6 inches) and bottoms out in February (2.6 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 30° | 3.1″ | 6 |
| February | 32° | 2.6″ | 6 |
| March | 40° | 3.2″ | 8 |
| April | 52° | 3.4″ | 9 |
| May | 62° | 4.1″ | 9 |
| June | 70° | 4.6″ | 8 |
| July | 74° | 3.9″ | 8 |
| August | 72° | 3.8″ | 7 |
| September | 65° | 3.5″ | 6 |
| October | 54° | 3.1″ | 8 |
| November | 43° | 3.0″ | 6 |
| December | 34° | 3.0″ | 7 |
Frequently asked
- When does it freeze in Heidelberg?
- Heidelberg's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Heidelberg?
- June is the wettest month with about 4.6 inches of rain on average; the city receives roughly 41 inches annually.
- What is the warmest month in Heidelberg?
- July is typically warmest, averaging about 74°F.
- What is the coldest month in Heidelberg?
- January is typically coldest, averaging about 30°F.
- When can I start a vegetable garden in Heidelberg?
- Cool-season crops (peas, lettuce) can be sown around the last spring frost (mid-April); warm-season crops (tomatoes, peppers) wait until 1–2 weeks after.
- How many rainy days does Heidelberg get?
- Heidelberg averages about 89 rainy days per year.
- What hardiness zone is Heidelberg?
- Heidelberg'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
Heidelberg, Pennsylvania sits in a warm-summer humid continental climate zone. January means hover near 30°F while July averages 74°F — a 44°F seasonal swing.
Across the year, Heidelberg receives about 41 inches of precipitation spread over roughly 89 rainy days.
The rhythm of the year is set by latitude (40.4°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.