Frost Advisory
Starts in 15 min
When
From midnight tonight to 9 AM EDT Saturday.
Where
Portions of central, northern, and southern New Jersey and southeast Pennsylvania.
Issued for this forecast zone · National Weather Service Mount Holly NJ
What, impacts and precautionsHide details
What
Temperatures as low as 33 degrees will result in frost formation.
Impacts
Frost could harm sensitive outdoor vegetation. Sensitive outdoor plants may be killed if left uncovered.
Precautionary actions
Take steps now to protect tender plants from the cold.
Areas: Middlesex; Western Monmouth; Mercer; Salem; Gloucester; Camden; Northwestern Burlington; Ocean; Cumberland; Atlantic; Southeastern Burlington; Delaware; Philadelphia; Eastern Chester; Eastern Montgomery; Lower Bucks
See it on weather.gov (opens in a new tab)

Observed 10:30 PM EDT at KPHL

Swarthmore, PA weather

Partly cloudy and 50°10°.

Forecasts agree

Now 50°10°

Partly cloudy

Wind: Calm; Up to 5 mph8 km/h through 11 AM
Dew point: 36°2°; Comfortable
UV tomorrow: 4Moderate; Moderate 11 AM–4 PM · peak 4
Air quality: 49Good; Main pollutant: PM2.5 (fine particles)
Pressure: 30.47 inHg1032 hPa; Rising slowly · +0.02 inHg+0.7 hPa in 3 h

No precipitation expected in the next 2 hours.

From forecast models

Next 48 hours

10°5° cooler than this time yesterday (61°16° then, 51°11° now)

Good hours for

Low 36°2° tomorrow at 6 AM
Above 50°10° tomorrow by 10 AM
High 63°17° tomorrow at 4 PM
Below 50°10° tomorrow night after 9 PM

TonightDown to 37°3° by 4 AM · Clear
Tomorrow morningUp to 55°13° by 11 AM · Partly cloudy
Tomorrow afternoonUp to 63°17° by 4 PM · Clear
Tomorrow nightDown to 38°3° by 4 AM · Clear
Sunday morningUp to 57°14° by 11 AM · Clear
Sunday afternoonUp to 66°19° by 4 PM · Clear
Sunday nightDown to 48°9° by 10 PM · Clear

Hourly forecast, next 48 hours, in the place's local time
Hour	Conditions	Temperature	Feels like	Precipitation	Wind	Humidity	Cloud cover	UV index
Fri 11p	Partly cloudy	42°6° (likely 42°6° to 48°9°)	42°6°	0%	0 mph0 km/h, gusts 3 mph5 km/h	79%	54%	0
Sat 12a	Clear	41°5° (likely 41°5° to 47°8°)	41°5°	0%	0 mph0 km/h, gusts 3 mph4 km/h	82%	17%	0
Sat 1a	Clear	40°4° (likely 40°4° to 46°8°)	40°4°	0%	0 mph0 km/h, gusts 3 mph5 km/h	85%	5%	0
Sat 2a	Clear	40°4° (likely 40°4° to 45°7°)	40°4°	0%	0 mph0 km/h, gusts 3 mph5 km/h	85%	0%	0
Sat 3a	Clear	38°3° (likely 38°3° to 43°6°)	38°3°	0%	0 mph0 km/h, gusts 4 mph6 km/h	89%	3%	0
Sat 4a	Clear	37°3° (likely 37°3° to 42°6°)	37°3°	0%	5 mph8 km/h from N, gusts 5 mph7 km/h	96%	7%	0
Sat 5a	Partly cloudy	37°3° (likely 37°3° to 41°5°)	34°1°	0%	5 mph8 km/h from N, gusts 6 mph9 km/h	92%	42%	0
Sat 6a	Mostly clear	36°2° (likely 36°2° to 40°4°)	33°1°	0%	5 mph8 km/h from N, gusts 6 mph9 km/h	96%	53%	0
Sat 7a	Mostly sunny	37°3° (likely 37°3° to 39°4°)	37°3°	0%	5 mph8 km/h from N, gusts 7 mph11 km/h	96%	30%	0
Sat 8a	Sunny	38°3° (likely 38°3° to 40°4°)	34°1°	0%	5 mph8 km/h from N, gusts 7 mph11 km/h	92%	23%	0
Sat 9a	Sunny	43°6° (likely 43°6° to 45°7°)	40°4°	0%	5 mph8 km/h from N, gusts 7 mph11 km/h	79%	17%	1
Sat 10a	Sunny	51°11° (likely 49°9° to 53°12°)	51°11°	0%	5 mph8 km/h from N, gusts 5 mph8 km/h	61%	20%	2
Sat 11a	Sunny	55°13° (likely 54°12° to 57°14°)	55°13°	0%	5 mph8 km/h from NE, gusts 4 mph7 km/h	53%	7%	3
Sat 12p	Sunny	58°14° (likely 57°14° to 60°16°)	58°14°	0%	5 mph8 km/h from NE, gusts 4 mph7 km/h	45%	4%	4
Sat 1p	Sunny	61°16° (likely 59°15° to 61°16°)	61°16°	0%	5 mph8 km/h from E, gusts 4 mph7 km/h	39%	7%	4
Sat 2p	Sunny	62°17° (likely 60°16° to 62°17°)	62°17°	0%	5 mph8 km/h from E, gusts 4 mph6 km/h	38%	10%	4
Sat 3p	Sunny	62°17° (likely 61°16° to 63°17°)	62°17°	0%	5 mph8 km/h from E, gusts 3 mph5 km/h	36%	7%	3
Sat 4p	Sunny	63°17° (likely 61°16° to 63°17°)	63°17°	0%	5 mph8 km/h from E, gusts 3 mph5 km/h	36%	3%	2
Sat 5p	Sunny	62°17° (likely 60°16° to 62°17°)	62°17°	0%	0 mph0 km/h, gusts 4 mph6 km/h	38%	0%	1
Sat 6p	Clear	60°16° (likely 56°13° to 60°16°)	60°16°	0%	0 mph0 km/h, gusts 4 mph6 km/h	42%	0%	0
Sat 7p	Clear	56°13° (likely 53°12° to 56°13°)	56°13°	0%	0 mph0 km/h, gusts 4 mph7 km/h	51%	0%	0
Sat 8p	Clear	50°10° (likely 50°10° to 53°12°)	50°10°	0%	0 mph0 km/h, gusts 6 mph9 km/h	66%	0%	0
Sat 9p	Clear	48°9° (likely 48°9° to 52°11°)	48°9°	0%	0 mph0 km/h, gusts 5 mph7 km/h	71%	0%	0
Sat 10p	Clear	46°8° (likely 46°8° to 50°10°)	46°8°	0%	0 mph0 km/h, gusts 5 mph9 km/h	79%	1%	0
Sat 11p	Clear	44°7° (likely 44°7° to 48°9°)	44°7°	0%	0 mph0 km/h, gusts 5 mph7 km/h	86%	0%	0
Sun 12a	Clear	43°6° (likely 43°6° to 47°8°)	43°6°	0%	0 mph0 km/h, gusts 4 mph6 km/h	89%	0%	0
Sun 1a	Clear	42°6° (likely 42°6° to 45°7°)	42°6°	0%	0 mph0 km/h, gusts 4 mph6 km/h	93%	0%	0
Sun 2a	Clear	41°5° (likely 41°5° to 45°7°)	41°5°	0%	0 mph0 km/h, gusts 4 mph6 km/h	96%	0%	0
Sun 3a	Clear	40°4° (likely 40°4° to 44°7°)	40°4°	0%	0 mph0 km/h, gusts 4 mph6 km/h	100%	0%	0
Sun 4a	Clear	38°3° (likely 38°3° to 44°7°)	38°3°	0%	0 mph0 km/h, gusts 4 mph7 km/h	100%	0%	0
Sun 5a	Clear	38°3° (likely 38°3° to 43°6°)	38°3°	0%	0 mph0 km/h, gusts 5 mph7 km/h	100%	0%	0
Sun 6a	Clear	37°3° (likely 37°3° to 42°6°)	37°3°	0%	0 mph0 km/h, gusts 5 mph9 km/h	100%	0%	0
Sun 7a	Sunny	37°3° (likely 37°3° to 41°5°)	37°3°	0%	0 mph0 km/h, gusts 5 mph8 km/h	100%	2%	0
Sun 8a	Sunny	39°4° (likely 38°3° to 41°5°)	39°4°	0%	0 mph0 km/h, gusts 5 mph8 km/h	100%	3%	0
Sun 9a	Sunny	45°7° (likely 44°7° to 47°8°)	45°7°	0%	0 mph0 km/h, gusts 5 mph8 km/h	82%	0%	1
Sun 10a	Sunny	51°11° (likely 51°11° to 54°12°)	51°11°	0%	0 mph0 km/h, gusts 2 mph4 km/h	66%	2%	2
Sun 11a	Sunny	57°14° (likely 57°14° to 59°15°)	57°14°	0%	0 mph0 km/h, gusts 5 mph8 km/h	55%	4%	3
Sun 12p	Sunny	61°16° (likely 60°16° to 62°17°)	61°16°	0%	0 mph0 km/h, gusts 5 mph8 km/h	46%	4%	4
Sun 1p	Sunny	63°17° (likely 61°16° to 64°18°)	63°17°	0%	0 mph0 km/h, gusts 4 mph7 km/h	43%	3%	4
Sun 2p	Sunny	64°18° (likely 62°17° to 65°18°)	64°18°	0%	0 mph0 km/h, gusts 5 mph8 km/h	40%	2%	4
Sun 3p	Sunny	65°18° (likely 63°17° to 65°18°)	65°18°	0%	0 mph0 km/h, gusts 5 mph9 km/h	38%	2%	3
Sun 4p	Sunny	66°19° (likely 63°17° to 66°19°)	66°19°	0%	0 mph0 km/h, gusts 5 mph8 km/h	37%	3%	2
Sun 5p	Sunny	64°18° (likely 62°17° to 65°18°)	64°18°	0%	0 mph0 km/h, gusts 5 mph7 km/h	40%	2%	1
Sun 6p	Clear	61°16° (likely 58°14° to 61°16°)	61°16°	0%	0 mph0 km/h, gusts 4 mph6 km/h	46%	0%	0
Sun 7p	Clear	56°13° (likely 55°13° to 57°14°)	56°13°	0%	0 mph0 km/h, gusts 4 mph7 km/h	57%	1%	0
Sun 8p	Clear	53°12° (likely 52°11° to 55°13°)	53°12°	0%	0 mph0 km/h, gusts 4 mph6 km/h	66%	0%	0
Sun 9p	Clear	50°10° (likely 49°9° to 56°13°)	50°10°	0%	0 mph0 km/h, gusts 2 mph4 km/h	74%	0%	0
Sun 10p	Clear	48°9° (likely 47°8° to 55°13°)	48°9°	0%	0 mph0 km/h, gusts 3 mph5 km/h	80%	0%	0

Days ahead

Shaded: typical range for these dates (1991–2020)

Today, Oct 23. Partly sunny. High 62°17°, low 36°2°. Typical 64°18° / 46°8°. Dry. Forecasts agree.
1. Overnight
  midnight–6 AM
  Clear, 37°3°
  Dry
Official NWS forecast
Tonight: Areas of frost after midnight. Partly cloudy, with a low around 36. North wind 0 to 5 mph.
Forecasts agreeIndependent forecasts are close; the range is narrow.
High, likely
61°16°–63°17°
Low, likely
36°2°–48°9°
Typical high / low
64°18° / 46°8°
Wind
13 mph20 km/h, gusts 25 mph40 km/h
UV peak
4
Tomorrow, Oct 24. Mostly sunny. High 63°17°, low 37°3°. Typical 64°18° / 46°8°. Dry. Forecasts agree.
1. Morning
  6 AM–noon
  Sunny, 38°3°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 63°17°
  Dry
3. Evening
  6 PM–midnight
  Clear, 50°10°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 38°3°
  Dry
Official NWS forecast
Day: Areas of frost before 10am. Sunny, with a high near 63. Northeast wind 0 to 5 mph.
Night: Patchy frost after 10pm. Mostly clear, with a low around 37. Northwest wind around 0 mph.
Forecasts agreeIndependent forecasts are close; the range is narrow.
High, likely
61°16°–63°17°
Low, likely
37°3°–39°4°
Typical high / low
64°18° / 46°8°
Wind
6 mph9 km/h
UV peak
4
Sunday, Oct 25. Sunny. High 66°19°, low 41°5°. Typical 64°18° / 46°8°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 39°4°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 66°19°
  Dry
3. Evening
  6 PM–midnight
  Clear, 53°12°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 45°7°
  Dry
Official NWS forecast
Day: Patchy frost before 9am. Sunny, with a high near 66. Northwest wind around 0 mph.
Night: Clear, with a low around 41. West wind around 0 mph.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
63°17°–66°19°
Low, likely
38°3°–41°5°
Typical high / low
64°18° / 46°8°
Wind
6 mph9 km/h
UV peak
4
Monday, Oct 26. Mostly sunny. High 69°21°, low 49°9°. Typical 63°17° / 45°7°. Dry. Forecasts agree.
1. Morning
  6 AM–noon
  Sunny, 46°8°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 68°20°
  Dry
3. Evening
  6 PM–midnight
  Clear, 57°14°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 52°11°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Sunny, with a high near 69.
Night: Mostly clear, with a low around 49.
Forecasts agreeIndependent forecasts are close; the range is narrow.
High, likely
67°19°–69°21°
Low, likely
42°6°–49°9°
Typical high / low
63°17° / 45°7°
Wind
7 mph11 km/h, gusts 17 mph27 km/h
UV peak
4
Tuesday, Oct 27. Mostly sunny. High 66°19°, low 45°7°. Typical 63°17° / 45°7°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 51°11°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 64°18°
  Dry
3. Evening
  6 PM–midnight
  Clear, 55°13°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 45°7°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Sunny, with a high near 66.
Night: Partly cloudy, with a low around 45.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
62°17°–67°19°
Low, likely
45°7°–51°11°
Typical high / low
63°17° / 45°7°
Wind
10 mph16 km/h, gusts 25 mph41 km/h
UV peak
4
Wednesday, Oct 28. Cloudy. High 63°17°, low 48°9°. Typical 63°17° / 45°7°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 44°7°
  Dry
2. Afternoon
  noon–6 PM
  Cloudy, 62°17°
  Dry
3. Evening
  6 PM–midnight
  Partly cloudy, 56°13°
  Dry
4. Overnight
  midnight–6 AM
  Cloudy, 49°10°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Mostly sunny, with a high near 63.
Night: Mostly cloudy, with a low around 48.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
60°16°–64°18°
Low, likely
41°5°–48°9°
Typical high / low
63°17° / 45°7°
Wind
8 mph13 km/h, gusts 17 mph28 km/h
UV peak
4
Thursday, Oct 29. Partly sunny. High 68°20°, low 52°11°. Typical 62°17° / 44°7°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 49°10°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 67°19°
  Dry
3. Evening
  6 PM–midnight
  Clear, 59°15°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 52°11°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Mostly sunny, with a high near 68.
Night: Partly cloudy, with a low around 52.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
64°18°–69°21°
Low, likely
46°8°–52°11°
Typical high / low
62°17° / 44°7°
Wind
8 mph13 km/h, gusts 29 mph47 km/h
UV peak
4
Friday, Oct 30. Sunny. High 70°21°, low 50°10°. Typical 62°17° / 44°7°. Dry. Forecasts differ.
1. Morning
  6 AM–noon
  Sunny, 51°11°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 69°20°
  Dry
3. Evening
  6 PM–midnight
  Clear, 58°15°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 50°10°
  Dry
Hours this far out come from computer models only.
Official NWS forecast
Day: Mostly sunny, with a high near 70.
Forecasts differIndependent forecasts disagree; expect changes and plan for the range.
High, likely
65°18°–73°23°
Low, likely
49°9°–51°11°
Typical high / low
62°17° / 44°7°
Wind
8 mph13 km/h, gusts 23 mph37 km/h
UV peak
4
Saturday, Oct 31. Sunny. High 69°21°, low 48°9°. Typical 62°17° / 44°7°. Dry. Mostly agree.
1. Morning
  6 AM–noon
  Sunny, 48°9°
  Dry
2. Afternoon
  noon–6 PM
  Sunny, 68°20°
  Dry
3. Evening
  6 PM–midnight
  Clear, 59°15°
  Dry
4. Overnight
  midnight–6 AM
  Clear, 48°9°
  Dry
Hours this far out come from computer models only.
The National Weather Service writes about seven days ahead; this day is our model forecast only.
Mostly agreeIndependent forecasts are fairly close; small surprises are possible.
High, likely
67°19°–71°22°
Low, likely
42°6°–56°13°
Typical high / low
62°17° / 44°7°
Wind
10 mph15 km/h, gusts 23 mph37 km/h
UV peak
4
Sunday, Nov 1. Cloudy. High 67°19°, low 49°9°. Typical 61°16° / 43°6°. Rain 0.01 in0.3 mm, 20% chance. Forecasts differ.
1. Morning
  6 AM–noon
  Sunny, 48°9°
  Dry
2. Afternoon
  noon–6 PM
  Cloudy, 66°19°
  20% chance
3. Evening
  6 PM–midnight
  Cloudy, 60°15°
  20% chance
Hours this far out come from computer models only.
The National Weather Service writes about seven days ahead; this day is our model forecast only.
Forecasts differIndependent forecasts disagree; expect changes and plan for the range.
High, likely
61°16°–71°22°
Low, likely
45°7°–55°13°
Typical high / low
61°16° / 43°6°
Wind
9 mph15 km/h, gusts 19 mph30 km/h
UV peak
4

10 days15 days30 days

The outlook

Today
Dry, high 62°, low 36°.
Tomorrow
Dry, high 63°, low 37°.
Sunday
Dry, high 66°, low 41°, warming up.
Rest of week
Mostly dry, highs 63–70°.

Want the meteorologists’ reasoning? Read the NWS forecast discussion (PHI) (opens in a new tab)

What changed since yesterday

No meaningful changes from yesterday’s forecast.

Radar

Radar data: NOAA MRMS, rendered by forecast.blue

Radar loads when scrolled into view

Full-screen radar

Rivers

NOAA river gauges within 25 mi

Schuylkill River at Philadelphia

9.6 mi

Below flood stage

Level: 6.1 ft
Flow: 1,060 cfs

Forecast peak 6.1 ft Sat 2 AM

Reading from Fri 10 PM · NWS gauge page

Schuylkill River near Philadelphia near 30th Street

9.7 mi

Below flood stage

Level: 4.1 ft

Forecast peak 4.8 ft Sat 12 AM

Reading from Fri 10:45 PM · NWS gauge page

Delaware River at USCG Station Washington Street (IN MLLW)

11 mi

Below flood stage

Level: 7.1 ft

Forecast peak 8.0 ft Sat 12 AM

Reading from Fri 10:54 PM · NWS gauge page

Brandywine Creek at Chadds Ford

13 mi

Below flood stage

Level: 1.9 ft
Flow: 207 cfs

Forecast peak 1.9 ft Sat 2 AM

Reading from Fri 10:30 PM · NWS gauge page

For your home

What this week’s weather means for heating, cooling, pipes and fresh air.

Heating this week

About 59% less heating than a typical week.

This week 31Typical 75

Heating degree days, base 65°F

Heat-pump hours, next 7 days

h below 47°F: 22
h below 17°F: 0
h below 5°F: 0

47, 17 and 5°F are the test points heat pumps are rated at. About 17 hours are near freezing and damp, when outdoor units defrost more often.

Comfort

Dry air outside (dew point 36°F).

Open the windows?

Sat, 1:00 PM–6:00 PM

Good stretch to open the windows.

Is this typical?

Philadelphia International Airport · official normals 1991–2020 · records 1873–2026

Oct 23, today vs a typical year

Today’s expected high is 2°1° colder than typical.

Last 7 days vs normal

On average 1°0° colder than normal (daily mean temperature).

−6°−3°SunOct 18
−2°−1°MonOct 19
+3°+1°TueOct 20
+2°+1°WedOct 21
+2°+1°ThuOct 22
—FriOct 23
—SatOct 24

Swarthmore weather by month: normals, records, snow and freeze dates

Sun & moon

Sun

Daylight: 10 h 50 min; Losing 2 min 30 s a day; shortest Dec 21, 1 h 30 min less
Golden hour: 5:33–6:27 PM; Morning 7:03–7:57 AM
Blue hour: 6:27–6:38 PM; Morning 6:52–7:03 AM; first light 6:52 AM

Stars tonight? Fair

Mostly clear 12–5 AM, but the moon is 95% lit and up.

Moon

Waxing gibbous

95% lit · growing

Today: sets 4:24 AM · rises 4:41 PM
Full moon: Oct 26
New moon: Nov 9

Looking west from Swarthmore. The highest point on the skyline is about 4,800 ft, 49 mi away.Skyline from USGS elevation data, heights drawn up to 6× taller. Sky, sun and moon as they are now.

1 active weather alert

Frost Advisory

Swarthmore, PA weather

Next 2 hours

Next 48 hours

Days ahead

The outlook

Today

Tomorrow

Sunday

Rest of week

What changed since yesterday

Radar

Rivers

Schuylkill River at Philadelphia

Schuylkill River near Philadelphia near 30th Street

Delaware River at USCG Station Washington Street (IN MLLW)

Brandywine Creek at Chadds Ford

For your home

Heating this week

Heat-pump hours, next 7 days

Comfort

Open the windows?

Is this typical?

Oct 23, today vs a typical year

Last 7 days vs normal

Sun & moon

Sun

Stars tonight? Fair

Moon