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Greencastle, Pennsylvania Weather

Cicadas claim the afternoon. Day 14 of summer. Read this microseason across nine climate regions →

Greencastle weather forecast — hour by hour, 7-day outlook, NOAA radar

Greencastle, PA
Saturday, July 4 at 8:17 AM
81
°
Clear
Feels like
86°
Humidity
61%
Wind
4 mph
Sunrise
1:48 AM
Sunset
4:42 PM
Greencastle, PA
Hour by hour · 24h
24-Hour ForecastGreencastle, PA: 24-hour forecast. Temperatures range from 74 to 101 degrees Fahrenheit with a 25% chance of precipitation at 9 PM.
L 74°H 101°
Greencastle, PA
7-day forecast
  1. Today
    Jul 4
    Overcast
    25%
    —
    101°75°—
  2. Sunday
    Jul 5
    Rain
    84%
    0.42″
    95°73°-6°
  3. Monday
    Jul 6
    Light Showers
    83%
    0.18″
    77°65°-18°
  4. Tuesday
    Jul 7
    Overcast
    68%
    —
    75°62°-2°
  5. Wednesday
    Jul 8
    Overcast
    16%
    —
    83°58°+8°
  6. Thursday
    Jul 9
    Overcast
    38%
    —
    91°64°+8°
  7. Friday
    Jul 10
    Light Drizzle
    35%
    —
    88°69°-3°
Greencastle, PA
Next 24 hours · Warm now
HOT 90°65°88°110°6a12p6p12anow 80°high 101°low 74°PRECIP %
Greencastle, PA
Anemometer · 24h winds · from true
NESW
From · True
SW
221° · veering 8°
Direction
SW
221°
Sustained
4
mph
Gust
12
mph
Peak 24h
25
avg 5
Beaufort · 2 · LIGHT BRZ
0
CALM
<1
1
LIGHT AIR
1–3
2
LIGHT BRZ
4–7
3
GENTLE BRZ
8–12
4
MOD BRZ
13–18
5
FRESH BRZ
19–24
6
STRONG BRZ
25–31
7
NEAR GALE
32–38
24h · sust vs gust · mph
avg 5 · pk 25 @ 2:00a
0102030MPHB1B2B3B4B5B6B7-21h-18h-15h-12h-9h-6h-3h-24hNOWpk 322SUSTGUST
−24h−18h−12h−6hnow
Light breeze veering 8° from the sw.
Greencastle, PA
Barometer · 24h pressure · mb
STORMRAINCHANGEFAIRDRY9901000101010201030
Pressure · mb
994.9
+0.8 mb in 3h · rising · 29.38 inHg
Now
994.9
mb
3h
+0.8
mb
12h
+1.0
mb
24h
-2.2
mb
Regime · STORM
STORM
RAIN
CHANGE
FAIR
DRY
24h · Pressure · mb
range 994–997
9859909951000STORM|RAIN10051010RAIN|CHG1015CHG|FAIR10201025FAIR|DRY1030-21h-18h-15h-12h-9h-6h-3h-24hNOW997.2993.6994.9
−24h−18h−12h−6hnow
Deep low — expect rough seas, strong wind, and persistent rain.
Greencastle, PA
Air quality
54
AQI
Moderate
→-2 in 6h▲Peak ~60 @ 6 PM

AQI 54 (Moderate), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 12.3 µg/m³ (AQI 57) with a 0.92 fine-to-coarse ratio and 4 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 during the projected peak around 6 PM.

PM 2.5DRIVERModerate
12.3μg/m³
PM 10Good
13μg/m³
NO₂Good
3μg/m³
OzoneModerate
100μg/m³
UV IndexLow
1.2

What's driving it

Ozone × UV × Sky

Ozone at AQI 47 now. With UV 4.0 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 25 around 1 PM.

Present
AQI 47
UV peak
4.0 at 1 PM
Sky at peak
clear
Projected peak
AQI 25

PM × Wind × Precip

PM2.5 at 12.3 µg/m³ (AQI 57) with a 0.92 fine-to-coarse ratio and 4 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).

7-DAY AQI TREND50100SATSUNMONTUEWEDTHUFRISAT7-DAY PM2.5 TREND · μg/m³310
Greencastle, PA
Sky cover · visibility · 24h
Cloud cover
0%
CLEAR
100%0%−24h−18h−12h−6hnow
Visibility
57.9mi
UNLIMITED
98 mi0 mi−24h−18h−12h−6hnow
Earth · GOES-19 ABI
Full Disk · Visible · GeoColor
GOES-19 full disk Visible · GeoColor
True-color daytime, blue/IR sandwich at night
12:17 UTC · Greencastle, PA · NOAA NESDIS / STAR · up to 10848 px
Continental US · GOES-19 ABI
CONUS Sector · Visible · GeoColor
GOES-19 CONUS Visible · GeoColor
Daytime true-color, blue-light/IR sandwich at night
12:17 UTC · Greencastle, PA · NOAA NESDIS / STAR · 5-min cadence · up to 10000 px
Greencastle, PA
Satellite · infrared · animated
Greencastle, PA
Loading IR frames…
IR · cloud-top temp© RainViewer · Carto
Greencastle, PA
Almanac · Saturday, July 4
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
Civil dawn
5:16 AM
Sunrise
1:48 AM
Daylight
14h 54m
Sunset
4:42 PM
Civil dusk
9:16 PM
Planting note
Harvest early potatoes. Begin drying onions on the surface.
Greencastle, PA
The moon
Waning Gibbous
82% illuminated
Moonrise
11:04 PM
Moonset
10:14 AM
In sign
♓︎ Pisces
Greencastle, PA
Microseason
Jul 1–5

Cicadas claim the afternoon

plant
Jan 151% of the yearDec 31

Read this microseason across nine climate regions →

Greencastle at a glance

  • Today vs. normal: 9°F above the seasonal normal for this latitude
  • Last frost: April 15 (climatological average for this latitude)
  • Microseason: Jul 1–5
  • Planting window: Harvest early potatoes. Begin drying onions on the surface.

ZIP code: 17225

16-Day Forecast — Greencastle

  1. Sat101°75°25%
  2. Sun95°73°84%
  3. Mon77°65°83%
  4. Tue75°62°68%
  5. Wed83°58°16%
  6. Thu91°64°38%
  7. Fri88°69°35%
  8. Sat85°69°35%
  9. Sun78°67°24%
  10. Mon79°63°18%
  11. Tue77°66°13%
  12. Wed88°66°23%
  13. Thu92°68°21%
  14. Fri94°71°30%
  15. Sat79°71°35%
  16. Sun87°68°32%

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 — Greencastle

SPC has placed Greencastle in the Slight Risk category for severe thunderstorms today.

  • TODAYSLGTSlight Risk
  • TOMORROWSLGTSlight 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.

January 1–5: The year turns in silence.January 6–10: Ice thickens on still water.January 11–15: Shortest shadows lengthen.January 16–20: Pheasants begin to call.January 21–25: Springs begin to thaw.January 26–31: Chickadees announce dawn.February 1–5: East wind softens the frost.February 6–10: Sap begins to rise.February 11–15: First snowdrops appear.February 16–20: Red-winged blackbirds return.February 21–25: Rain begins to replace snow.February 26–28: Skunk cabbage pushes through ice.March 1–5: Ice withdraws from the reservoir.March 6–10: Crocuses open to weak sun.March 11–15: Peepers call from the marsh.March 16–20: Woodcocks spiral at dusk.March 21–25: Equinox — light overtakes dark.March 26–31: Forsythia opens along the fences.April 1–5: Cherry blossoms drift like snow.April 6–10: Warblers appear in the understory.April 11–15: Magnolias bloom and fall in a day.April 16–20: Dogwoods float above the forest.April 21–25: Lilacs perfume the evening.April 26–30: Last frost releases the garden.May 1–5: Warblers flood the Ramble.May 6–10: Tulip poplars light their candles.May 11–15: Shad run up the rivers.May 16–20: Roses open along the stoops.May 21–25: Firefly scouts appear at dusk.May 26–31: Strawberries ripen in the sun.June 1–5: Fireflies rise from the lawn.June 6–10: Elderflowers open in hedgerows.June 11–15: Solstice approaches — longest light.June 16–20: Honeysuckle sweetens the night.June 21–25: Solstice — the sun stands still.June 26–30: Lightning bugs drift through oaks.July 1–5: Cicadas claim the afternoon.July 6–10: Queen Anne's lace lines the roads.July 11–15: Thunder builds each afternoon.July 16–20: Corn reaches for the tassels.July 21–25: Dog days settle in the haze.July 26–31: Katydids begin their chorus.August 1–5: Night falls a minute earlier.August 6–10: Sunflowers face the morning.August 11–15: Goldenrod begins to bloom.August 16–20: Crickets pulse through warm nights.August 21–25: First cool morning surprises.August 26–31: Monarchs stage for flight.September 1–5: School buses reappear.September 6–10: Asters purple the roadsides.September 11–15: Hawk migration over the Hudson.September 16–20: Equinox — dark overtakes light.September 21–25: Apples hang heavy on the branch.September 26–30: Geese begin to chevron south.October 1–5: Witch hazel blooms as others fade.October 6–10: Maples begin to blaze.October 11–15: Frost paints the garden black.October 16–20: Oaks turn bronze and russet.October 21–25: Leaves rattle down the gutters.October 26–31: Clocks fall back — dusk at five.November 1–5: Ginkgos drop overnight.November 6–10: Last leaves cling stubbornly.November 11–15: Juncos arrive from the north.November 16–20: Bare branches reveal the sky.November 21–25: First flurries dust the rooftops.November 26–30: Woodsmoke curls through the block.December 1–5: Darkness settles before dinner.December 6–10: Holly and winterberry persist.December 11–15: Shortest day approaches.December 16–20: Ice begins to form at the edges.December 21–25: Solstice — the sun begins return.December 26–31: The year turns in silence.🌱February 14 — First skunk-cabbage spathes thaw their way up☀️March 20 — Spring equinox — day and night balance🌸April 5 — Cherry blossoms peak in the parks🐦May 10 — Warbler migration peaks along the coast✨May 25 — First fireflies scout the meadows at dusk🌞June 21 — Summer solstice — longest day🦗July 25 — Peak cicada chorus in the afternoons🌊August 18 — Warmest sea-surface temperatures of the year🍂September 22 — Autumn equinox — the slow turn❄️October 25 — First widespread frost in the suburbs🍁November 10 — Peak leaf color across the Hudson Valley🌙December 21 — Winter solstice — longest night

Microseason · July 1–5

Cicadas claim the afternoon

Annual cicada buzz begins, peaking in the heat of the day.

Day 185 of 365 · Wedge 37 of 72

The solar year drawn as a wheel of 72 five-day windows. Each wedge is one microseason; the four colored arcs mark winter, spring, summer, and autumn; the small icons sit at notable phenological events. The crimson pointer creeps clockwise as the year turns.

Planting calendar

MonthPlantHarvest
January——
February——
March——
Aprillettuce, peas, spinach, radishes—
Maylettuce, peas, spinach, radishes, tomatoes, peppers, beans, squashlettuce, peas, radishes
Junetomatoes, peppers, beans, squashlettuce, peas, radishes
Julytomatoes, peppers, beans, squashtomatoes, beans, summer squash
August—tomatoes, beans, summer squash
Septemberfall brassicas, garlic (overwinter), carrotstomatoes, beans, summer squash
Octoberfall brassicas, garlic (overwinter), carrotswinter squash, tomatoes (last)
November——
December——

A year in weather

In Greencastle, July runs warmest near 78°F and January coldest around 33°F, while September is the wettest month (3.8 inches) and February the driest (2.0 inches).

MonthMean tempPrecipRainy days
January33°2.5″5
February36°2.0″5
March43°3.0″6
April55°3.3″7
May64°3.5″8
June73°3.4″7
July78°2.9″6
August75°2.9″6
September68°3.8″6
October57°2.8″5
November46°2.6″5
December37°2.8″5

Regional context

Greencastle's climate, from NOAA NCEI 1991-2020 station normals, pairs 33°F Januarys with 78°F Julys — a 45°F swing. About 35.6 inches of precipitation falls over roughly 71 days a year.

Greencastle's precipitation spreads evenly: September peaks at 3.8 inches on 6.2 wet days, while February holds 2.0 inches over 4.9 — no month dominates Greencastle's rain calendar. It is a balanced pattern Greencastle shares with places like State Line, PA, Marion, PA and Waynesboro, PA.

By mid-April the frosts ease in Greencastle, opening the season for peas, lettuce, spinach, and radishes. In Greencastle, warm-season transplants — tomatoes, peppers, basil — wait two weeks past Greencastle's frost date. Around mid-November, freezing nights resume in Greencastle and tender crops must come in. In Greencastle, low spots run 4-7°F colder than nearby slopes, nudging Greencastle's frost dates a week.

Similar climates: State Line, PA, Marion, PA, Waynesboro, PA, Mont Alto, PA, Mercersburg, PA.

Frequently asked

When does it freeze in Greencastle?
Greencastle's last spring frost lands near mid-April, and in Greencastle the first fall frost follows around mid-November.
What is the rainy season in Greencastle?
September is the wettest month in Greencastle, about 3.8 inches on average; the year totals roughly 36 inches.
What is the warmest month in Greencastle?
July is Greencastle's warmest month, averaging about 78°F.
What is the coldest month in Greencastle?
Greencastle bottoms out in January, with a mean near 33°F.
When can I start a vegetable garden in Greencastle?
Time tomatoes in Greencastle for two weeks after mid-April; peas and greens start at Greencastle's frost line.
How many rainy days does Greencastle get?
Expect roughly 71 wet days a year in Greencastle.
What hardiness zone is Greencastle?
Greencastle's USDA zone comes from its January mean (33°F); enter the ZIP on the USDA lookup for the number.
What is the 10-day forecast for Greencastle?
Greencastle's extended outlook — daily high and low temperatures and precipitation chances for each upcoming day — is in the daily forecast above.
Will it rain this week in Greencastle?
See this week's day-by-day rain chances for Greencastle in the daily forecast above, and the next 24 hours in the hourly chart.
What is the weather like right now in Greencastle?
Current conditions for Greencastle and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
How often is the Greencastle forecast updated?
The Greencastle forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
When are sunrise and sunset in Greencastle?
Today's sunrise and sunset times for Greencastle are in the Almanac section above, along with civil dawn, civil dusk, and day length. Day length is longest near the summer solstice and shortest near the winter solstice.
How accurate is the weather forecast for Greencastle?
The next few days in Greencastle's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.

Climate

Greencastle, Pennsylvania occupies a warm-summer humid continental zone, with January means near 33°F and July around 78°F — a 45°F swing.

Greencastle sees close to 36 inches of precipitation annually, falling across some 71 wet days.

The 45°F gap between Greencastle's summer and winter, at 39.8°N, shapes Greencastle's frost calendar.

All cities in Pennsylvania →

Hagerstown, MD weather →

ZIP codes in Greencastle

  • 17225

Climate normals from the Open-Meteo Climate API. Köppen approximation from NOAA NCEI U.S. Climate Regions. See methodology for data sources, editorial rules, and corrections. Maintainer: Brian Tighe.