Greencastle, Pennsylvania Weather
Fireflies rise from the lawn. Day 76 of spring. Read this microseason across nine climate regions →
Greencastle weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Mostly Clear——81°50°—
- ThursdayJun 4Overcast——84°58°+3°
- FridayJun 5Overcast——84°62°0°
- SaturdayJun 6Light Drizzle24%—86°63°+2°
- SundayJun 7Showers50%—78°63°-8°
- MondayJun 8Overcast——73°56°-5°
- TuesdayJun 9Partly Cloudy11%—75°49°+2°
Ozone at AQI 49 now. AQI up 18 in the last 6 hours — air quality is degrading. With UV 0.2 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 12 by mid-afternoon.
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 49 now. With UV 0.2 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 12 by mid-afternoon.
- Present
- AQI 49
- UV peak
- 0.2 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 12
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
- 3:00 AM
- Moonset
- 12:08 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
Greencastle at a glance
- Today vs. normal: 3°F above the seasonal normal for this latitude
- Last frost: April 15 (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 3, 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
Greencastle's warmest month is July (~76°F mean) and its coldest is January (~31°F). Rainfall peaks in September (4.8 inches) and bottoms out in February (2.7 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 31° | 3.2″ | 11 |
| February | 34° | 2.7″ | 9 |
| March | 42° | 3.9″ | 13 |
| April | 53° | 3.9″ | 13 |
| May | 64° | 4.3″ | 14 |
| June | 72° | 3.4″ | 11 |
| July | 76° | 3.7″ | 12 |
| August | 75° | 3.7″ | 12 |
| September | 67° | 4.8″ | 16 |
| October | 55° | 3.4″ | 11 |
| November | 44° | 2.9″ | 10 |
| December | 36° | 3.7″ | 12 |
Regional context
Greencastle sits within a warm-summer humid continental climate region — a cohort that shares similar temperature ranges, seasonal patterns, and growing conditions across nearby cities.
Similar climates: Philadelphia, PA, Pittsburgh, PA, Allentown, PA, Harrisburg, PA, Lancaster, PA.
Frequently asked
- When does it freeze in Greencastle?
- Greencastle's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Greencastle?
- September is the wettest month with about 4.8 inches of rain on average; the city receives roughly 44 inches annually.
- What is the warmest month in Greencastle?
- July is typically warmest, averaging about 76°F.
- What is the coldest month in Greencastle?
- January is typically coldest, averaging about 31°F.
- When can I start a vegetable garden in Greencastle?
- 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 Greencastle get?
- Greencastle averages about 144 rainy days per year.
- What hardiness zone is Greencastle?
- Greencastle'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
Greencastle, Pennsylvania sits in a warm-summer humid continental climate zone. January means hover near 31°F while July averages 76°F — a 45°F seasonal swing.
Across the year, Greencastle receives about 44 inches of precipitation spread over roughly 144 rainy days.
The rhythm of the year is set by latitude (39.8°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.