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Climate of Pennsylvania facts for kids

Kids Encyclopedia Facts
Köppen Climate Types Pennsylvania
The Köppen climate types of Pennsylvania based on 1991-2020 climate normals

The climate of Pennsylvania is diverse due to the multitude of geographic features found within the state. Straddling two major climate zones, the southeastern corner of Pennsylvania has the warmest climate. A portion of Greater Philadelphia lies at the southernmost tip of the humid continental climate zone, with the city proper being in the humid subtropical climate zone. Still, Philadelphia features colder, snowier winters than most locations with a humid subtropical climate. Moving west toward the mountainous interior of the state, the climate becomes markedly colder, the number of cloudy days increases, and winter snowfall amounts are greater.

Using the January freezing isotherm, the humid subtropical climate (Cfa) only exists in parts of Greater Philadelphia and low-lying areas of the lower Susquehanna Valley from Harrisburg downriver. Pennsylvania's hardiness zone ranges from 5a in high-elevation areas to 7b in parts of Delaware and Philadelphia Counties.

Precipitation

Western areas of the state, particularly cities near Lake Erie, can receive over 100 inches (254 cm) of snowfall annually, and the entire state receives an average of 41 inches (1,041 mm) of rainfall every year. Floods are more common in March and April than other months of the year.

Tropical cyclones

Tropical cyclones normally threaten the states during the summer and fall, with their main impact being rainfall. Although Hurricane Agnes was barely a hurricane at landfall in Florida, its major impact was over the Mid-Atlantic region, where Agnes combined with a non-tropical low to produce widespread rains of 6 inches (150 mm) to 12 inches (300 mm) with local amounts up to 19 inches (480 mm) in western Schuylkill County in Pennsylvania. These rains produced widespread severe flooding from Virginia northward to New York, with other flooding occurring over the western portions of the Carolinas.

Philadelphia has received sustained winds approaching hurricane-force from tropical cyclones in the past.

Climate extremes

Temperature

The state record low is −42 °F (−41 °C), recorded at Smethport on January 5, 1904, while the state record high is 111 °F (44 °C), recorded at Phoenixville on July 9 and 10, 1936.

Climate data for Pennsylvania
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 85
(29)
83
(28)
92
(33)
98
(37)
102
(39)
107
(42)
111
(44)
108
(42)
106
(41)
100
(38)
88
(31)
82
(28)
111
(44)
Record low °F (°C) −42
(−41)
−39
(−39)
−31
(−35)
−5
(−21)
10
(−12)
20
(−7)
28
(−2)
23
(−5)
17
(−8)
7
(−14)
−15
(−26)
−29
(−34)
−42
(−41)
Source: https://climate.met.psu.edu/data/state/staterecords.php

Precipitation

Rain

Event Measurement Date Location
Greatest 24-Hour Rainfall 13.50 inches (343 mm) June 22, 1972
(during Hurricane Agnes)
York

Note: While the official measured rainfall record is given above, the NCDC notes that an estimated 34.50 inches (876 mm) of rain fell in 12 hours near Smethport on July 17, 1942. The NCDC says this is "arguably the greatest 24-hour rainfall on record outside of the tropics".

Snow

Event Measurement Date Location
Greatest 24-hour snowfall 38.0 inches (97 cm) March 20, 1958 Morgantown
Greatest two-day snowfall 60.5 inches (154 cm) December 24–26, 2017 Erie
Greatest snow depth 60.0 inches (152 cm) March 22 & 23, 1958 Gouldsboro

Hurricanes

Event Measurement Date Location
Wettest Tropical Cyclone 19.00 inches (483 mm) Agnes (1972) Western Schuylkill County

Climate statistics for selected cities

Climate data for Allentown, Pennsylvania (Lehigh Valley Int'l), 1981–2010 normals, extremes 1922–present
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 72
(22)
77
(25)
87
(31)
93
(34)
97
(36)
100
(38)
105
(41)
100
(38)
99
(37)
92
(33)
81
(27)
72
(22)
105
(41)
Mean maximum °F (°C) 57.9
(14.4)
59.6
(15.3)
71.6
(22.0)
82.5
(28.1)
88.2
(31.2)
91.9
(33.3)
94.2
(34.6)
92.5
(33.6)
88.0
(31.1)
79.0
(26.1)
70.6
(21.4)
59.7
(15.4)
95.4
(35.2)
Mean daily maximum °F (°C) 36.0
(2.2)
39.8
(4.3)
49.4
(9.7)
61.3
(16.3)
71.5
(21.9)
80.1
(26.7)
84.2
(29.0)
82.4
(28.0)
74.9
(23.8)
63.6
(17.6)
52.5
(11.4)
40.5
(4.7)
61.4
(16.3)
Mean daily minimum °F (°C) 19.5
(−6.9)
21.7
(−5.7)
28.8
(−1.8)
38.5
(3.6)
48.3
(9.1)
58.1
(14.5)
62.7
(17.1)
60.9
(16.1)
52.9
(11.6)
41.3
(5.2)
32.9
(0.5)
24.0
(−4.4)
40.8
(4.9)
Mean minimum °F (°C) 3.0
(−16.1)
5.7
(−14.6)
13.1
(−10.5)
26.0
(−3.3)
35.5
(1.9)
46.3
(7.9)
52.6
(11.4)
49.8
(9.9)
39.2
(4.0)
28.8
(−1.8)
19.9
(−6.7)
9.1
(−12.7)
0.2
(−17.7)
Record low °F (°C) −15
(−26)
−12
(−24)
−5
(−21)
12
(−11)
28
(−2)
39
(4)
46
(8)
41
(5)
30
(−1)
21
(−6)
3
(−16)
−8
(−22)
−15
(−26)
Average precipitation inches (mm) 3.03
(77)
2.70
(69)
3.39
(86)
3.56
(90)
4.14
(105)
4.31
(109)
4.95
(126)
3.69
(94)
4.62
(117)
3.88
(99)
3.50
(89)
3.58
(91)
45.35
(1,152)
Average snowfall inches (cm) 10.0
(25)
11.1
(28)
4.9
(12)
1.0
(2.5)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0.7
(1.8)
5.2
(13)
32.9
(84)
Average precipitation days (≥ 0.01 in) 11.1 9.8 11.0 12.1 12.1 11.4 10.9 9.5 9.1 9.1 9.8 10.9 126.8
Average snowy days (≥ 0.1 in) 5.6 4.8 2.5 0.4 0 0 0 0 0 0 0.6 3.5 17.4
Average relative humidity (%) 69.1 66.7 62.6 60.9 65.6 67.9 68.8 71.9 74.0 71.8 70.5 71.4 68.4
Source: NOAA (relative humidity 1961–1990)
Climate data for Erie, Pennsylvania (Erie International Airport), 1991–2020 normals, extremes 1873–present
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 73
(23)
77
(25)
82
(28)
89
(32)
91
(33)
100
(38)
99
(37)
96
(36)
99
(37)
89
(32)
82
(28)
75
(24)
100
(38)
Mean maximum °F (°C) 59
(15)
59
(15)
69
(21)
80
(27)
85
(29)
90
(32)
91
(33)
90
(32)
87
(31)
79
(26)
68
(20)
60
(16)
92
(33)
Mean daily maximum °F (°C) 35.2
(1.8)
36.5
(2.5)
44.3
(6.8)
56.8
(13.8)
68.3
(20.2)
77.1
(25.1)
81.1
(27.3)
79.9
(26.6)
73.7
(23.2)
62.3
(16.8)
50.5
(10.3)
40.2
(4.6)
58.8
(14.9)
Daily mean °F (°C) 28.2
(−2.1)
28.9
(−1.7)
36.1
(2.3)
47.4
(8.6)
58.8
(14.9)
68.2
(20.1)
72.7
(22.6)
71.5
(21.9)
65.2
(18.4)
54.3
(12.4)
43.6
(6.4)
34.1
(1.2)
50.8
(10.4)
Mean daily minimum °F (°C) 21.3
(−5.9)
21.4
(−5.9)
27.9
(−2.3)
38.0
(3.3)
49.3
(9.6)
59.4
(15.2)
64.2
(17.9)
63.2
(17.3)
56.7
(13.7)
46.3
(7.9)
36.7
(2.6)
28.0
(−2.2)
42.7
(5.9)
Mean minimum °F (°C) 4
(−16)
4
(−16)
11
(−12)
26
(−3)
35
(2)
46
(8)
54
(12)
53
(12)
44
(7)
34
(1)
24
(−4)
13
(−11)
0
(−18)
Record low °F (°C) −18
(−28)
−18
(−28)
−9
(−23)
7
(−14)
26
(−3)
32
(0)
44
(7)
37
(3)
33
(1)
23
(−5)
6
(−14)
−11
(−24)
−18
(−28)
Average precipitation inches (mm) 3.41
(87)
2.52
(64)
3.08
(78)
3.47
(88)
3.50
(89)
3.70
(94)
3.33
(85)
3.35
(85)
4.32
(110)
4.38
(111)
3.75
(95)
4.17
(106)
42.98
(1,092)
Average snowfall inches (cm) 31.8
(81)
19.4
(49)
14.5
(37)
2.6
(6.6)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
0.0
(0.0)
0.1
(0.25)
9.6
(24)
26.3
(67)
104.3
(265)
Average precipitation days (≥ 0.01 in) 19.7 15.4 14.3 14.0 13.5 11.5 10.5 10.2 10.1 14.3 14.9 18.5 166.9
Average snowy days (≥ 0.1 in) 16.3 12.3 7.8 2.3 0.0 0.0 0.0 0.0 0.0 0.2 4.8 11.5 55.2
Average relative humidity (%) 74.5 75.4 71.9 67.9 68.9 71.3 71.7 74.0 74.5 71.1 72.3 75.0 72.4
Source: NOAA (relative humidity 1961–1990)
Climate data for Harrisburg, Pennsylvania (Harrisburg Int'l), 1981–2010 normals, extremes 1888–present
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 73
(23)
78
(26)
87
(31)
93
(34)
97
(36)
100
(38)
107
(42)
104
(40)
102
(39)
97
(36)
84
(29)
75
(24)
107
(42)
Mean daily maximum °F (°C) 37.0
(2.8)
40.7
(4.8)
50.4
(10.2)
62.4
(16.9)
72.1
(22.3)
81.0
(27.2)
85.5
(29.7)
83.4
(28.6)
75.6
(24.2)
64.1
(17.8)
53.1
(11.7)
41.3
(5.2)
62.2
(16.8)
Mean daily minimum °F (°C) 22.8
(−5.1)
25.1
(−3.8)
33.0
(0.6)
41.9
(5.5)
52.1
(11.2)
62.0
(16.7)
66.3
(19.1)
64.5
(18.1)
56.2
(13.4)
44.6
(7.0)
35.1
(1.7)
26.6
(−3.0)
44.2
(6.8)
Record low °F (°C) −22
(−30)
−13
(−25)
−1
(−18)
11
(−12)
31
(−1)
40
(4)
49
(9)
45
(7)
30
(−1)
23
(−5)
10
(−12)
−8
(−22)
−22
(−30)
Average precipitation inches (mm) 2.88
(73)
2.39
(61)
3.37
(86)
3.10
(79)
3.79
(96)
3.60
(91)
4.61
(117)
3.20
(81)
4.07
(103)
3.27
(83)
3.23
(82)
3.23
(82)
40.74
(1,035)
Average snowfall inches (cm) 8.8
(22)
10.5
(27)
5.2
(13)
0.4
(1.0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0.6
(1.5)
5.1
(13)
30.6
(78)
Average precipitation days (≥ 0.01 in) 10.6 9.9 10.9 10.8 12.2 11.1 10.7 9.1 9.2 8.8 9.0 9.7 122.0
Average snowy days (≥ 0.1 in) 5.2 5.0 2.6 0.3 0 0 0 0 0 0 0.9 2.8 16.8
Average relative humidity (%) 64.4 63.2 60.7 59.2 65.2 67.7 68.6 72.2 73.8 70.5 68.2 66.4 66.7
Mean monthly sunshine hours 154.9 167.2 213.8 235.7 266.7 288.5 310.1 285.4 226.7 199.2 139.6 126.0 2,613.8
Percent possible sunshine 52 56 58 59 60 64 68 67 61 58 47 43 59
Source: NOAA (relative humidity and sun 1961–1990 at Capital City Airport)
Climate data for Philadelphia (Philadelphia Airport), 1981–2010 normals, extremes 1872–present
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 74
(23)
79
(26)
87
(31)
95
(35)
97
(36)
102
(39)
104
(40)
106
(41)
102
(39)
96
(36)
84
(29)
73
(23)
106
(41)
Mean maximum °F (°C) 62.0
(16.7)
62.7
(17.1)
73.6
(23.1)
83.2
(28.4)
89.1
(31.7)
94.2
(34.6)
96.4
(35.8)
94.7
(34.8)
89.8
(32.1)
81.7
(27.6)
72.3
(22.4)
63.5
(17.5)
97.5
(36.4)
Mean daily maximum °F (°C) 40.3
(4.6)
43.8
(6.6)
52.7
(11.5)
63.9
(17.7)
73.8
(23.2)
82.7
(28.2)
87.1
(30.6)
85.3
(29.6)
78.0
(25.6)
66.6
(19.2)
56.0
(13.3)
44.8
(7.1)
64.6
(18.1)
Daily mean °F (°C) 33.0
(0.6)
35.7
(2.1)
43.5
(6.4)
54.0
(12.2)
63.9
(17.7)
73.3
(22.9)
78.1
(25.6)
76.6
(24.8)
69.1
(20.6)
57.5
(14.2)
47.6
(8.7)
37.5
(3.1)
55.9
(13.3)
Mean daily minimum °F (°C) 25.6
(−3.6)
27.7
(−2.4)
34.4
(1.3)
44.1
(6.7)
54.0
(12.2)
63.8
(17.7)
69.2
(20.7)
67.9
(19.9)
60.3
(15.7)
48.4
(9.1)
39.2
(4.0)
30.1
(−1.1)
47.1
(8.4)
Mean minimum °F (°C) 8.7
(−12.9)
12.7
(−10.7)
19.4
(−7.0)
31.6
(−0.2)
42.0
(5.6)
52.2
(11.2)
59.8
(15.4)
57.8
(14.3)
47.2
(8.4)
35.8
(2.1)
26.0
(−3.3)
15.8
(−9.0)
6.4
(−14.2)
Record low °F (°C) −7
(−22)
−11
(−24)
5
(−15)
14
(−10)
28
(−2)
44
(7)
51
(11)
44
(7)
35
(2)
25
(−4)
8
(−13)
−5
(−21)
−11
(−24)
Average precipitation inches (mm) 3.03
(77)
2.65
(67)
3.79
(96)
3.56
(90)
3.71
(94)
3.43
(87)
4.35
(110)
3.50
(89)
3.78
(96)
3.18
(81)
2.99
(76)
3.56
(90)
41.53
(1,055)
Average snowfall inches (cm) 6.5
(17)
8.8
(22)
2.9
(7.4)
0.5
(1.3)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0.3
(0.76)
3.4
(8.6)
22.4
(57)
Average precipitation days (≥ 0.01 in) 10.6 9.4 10.5 11.3 11.1 9.8 9.9 8.4 8.7 8.6 9.3 10.6 118.2
Average snowy days (≥ 0.1 in) 4.4 3.6 1.8 0.4 0 0 0 0 0 0 0.2 1.8 12.2
Average relative humidity (%) 66.2 63.6 61.7 60.4 65.4 67.8 69.6 70.4 71.6 70.8 68.4 67.7 67.0
Mean monthly sunshine hours 155.7 154.7 202.8 217.0 245.1 271.2 275.6 260.1 219.3 204.5 154.7 137.7 2,498.4
Percent possible sunshine 52 52 55 55 55 61 61 61 59 59 52 47 56
Source: NOAA (relative humidity and sun 1961–1990)
Climate data for Pittsburgh (Pittsburgh International Airport), 1981–2010 normals, extremes 1871–present
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 75
(24)
77
(25)
84
(29)
90
(32)
95
(35)
98
(37)
103
(39)
103
(39)
102
(39)
91
(33)
82
(28)
74
(23)
103
(39)
Mean maximum °F (°C) 59.7
(15.4)
61.9
(16.6)
74.9
(23.8)
81.5
(27.5)
85.7
(29.8)
90.0
(32.2)
91.3
(32.9)
90.5
(32.5)
87.2
(30.7)
79.0
(26.1)
71.5
(21.9)
61.3
(16.3)
92.7
(33.7)
Mean daily maximum °F (°C) 35.7
(2.1)
39.3
(4.1)
49.2
(9.6)
61.7
(16.5)
70.8
(21.6)
79.1
(26.2)
82.5
(28.1)
81.4
(27.4)
74.3
(23.5)
62.6
(17.0)
51.2
(10.7)
39.4
(4.1)
60.6
(15.9)
Mean daily minimum °F (°C) 21.1
(−6.1)
23.0
(−5.0)
30.0
(−1.1)
40.2
(4.6)
49.3
(9.6)
58.4
(14.7)
62.8
(17.1)
61.5
(16.4)
54.0
(12.2)
42.9
(6.1)
34.7
(1.5)
25.3
(−3.7)
41.9
(5.5)
Mean minimum °F (°C) −0.1
(−17.8)
3.6
(−15.8)
10.9
(−11.7)
24.6
(−4.1)
34.8
(1.6)
44.1
(6.7)
50.7
(10.4)
49.6
(9.8)
39.3
(4.1)
29.0
(−1.7)
18.9
(−7.3)
6.7
(−14.1)
−3.9
(−19.9)
Record low °F (°C) −22
(−30)
−20
(−29)
−5
(−21)
11
(−12)
26
(−3)
34
(1)
42
(6)
39
(4)
31
(−1)
16
(−9)
−1
(−18)
−12
(−24)
−22
(−30)
Average precipitation inches (mm) 2.70
(69)
2.39
(61)
2.95
(75)
3.11
(79)
3.95
(100)
4.30
(109)
3.83
(97)
3.48
(88)
3.11
(79)
2.29
(58)
3.23
(82)
2.85
(72)
38.19
(970)
Average snowfall inches (cm) 11.5
(29)
10.2
(26)
7.4
(19)
1.5
(3.8)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0.4
(1.0)
2.1
(5.3)
8.3
(21)
41.4
(105)
Average precipitation days (≥ 0.01 in) 16.2 13.6 14.0 13.8 13.3 12.1 10.2 9.8 9.8 10.5 12.8 15.1 151.2
Average snowy days (≥ 0.1 in) 11.4 8.3 5.9 2.0 0 0 0 0 0 0.3 3.0 8.5 39.4
Average relative humidity (%) 69.9 67.3 64.1 59.8 63.4 66.2 68.8 71.2 72.0 68.3 70.2 71.9 67.8
Mean monthly sunshine hours 93.9 108.5 155.4 182.8 217.4 242.2 254.9 228.4 196.7 167.3 99.4 74.4 2,021.3
Percent possible sunshine 31 36 42 46 49 54 56 54 53 48 33 26 45
Source: NOAA (relative humidity and sun 1961–1990)
Climate data for Wilkes-Barre/Scranton Int'l Airport, Pennsylvania (1981–2010 normals, extremes 1901–present )
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Record high °F (°C) 69
(21)
76
(24)
85
(29)
93
(34)
93
(34)
99
(37)
103
(39)
102
(39)
100
(38)
91
(33)
81
(27)
71
(22)
103
(39)
Mean maximum °F (°C) 55.4
(13.0)
56.4
(13.6)
69.6
(20.9)
81.3
(27.4)
86.6
(30.3)
89.8
(32.1)
91.8
(33.2)
90.0
(32.2)
85.7
(29.8)
77.3
(25.2)
68.7
(20.4)
57.5
(14.2)
93.4
(34.1)
Mean daily maximum °F (°C) 33.2
(0.7)
36.8
(2.7)
46.2
(7.9)
59.1
(15.1)
69.7
(20.9)
77.7
(25.4)
81.9
(27.7)
79.9
(26.6)
72.3
(22.4)
60.7
(15.9)
49.4
(9.7)
37.5
(3.1)
58.8
(14.9)
Mean daily minimum °F (°C) 18.5
(−7.5)
20.7
(−6.3)
27.6
(−2.4)
38.2
(3.4)
47.6
(8.7)
56.5
(13.6)
60.9
(16.1)
59.5
(15.3)
52.1
(11.2)
41.1
(5.1)
33.3
(0.7)
23.8
(−4.6)
40.1
(4.5)
Mean minimum °F (°C) −0.8
(−18.2)
3.2
(−16.0)
9.1
(−12.7)
24.0
(−4.4)
34.4
(1.3)
43.1
(6.2)
49.4
(9.7)
47.1
(8.4)
37.5
(3.1)
28.3
(−2.1)
18.9
(−7.3)
5.9
(−14.5)
−3.1
(−19.5)
Record low °F (°C) −21
(−29)
−19
(−28)
−4
(−20)
8
(−13)
27
(−3)
34
(1)
43
(6)
38
(3)
29
(−2)
19
(−7)
6
(−14)
−13
(−25)
−21
(−29)
Average precipitation inches (mm) 2.37
(60)
2.03
(52)
2.55
(65)
3.33
(85)
3.52
(89)
4.03
(102)
3.79
(96)
3.41
(87)
4.07
(103)
3.34
(85)
3.14
(80)
2.68
(68)
38.26
(972)
Average snowfall inches (cm) 14.2
(36)
9.3
(24)
9.0
(23)
3.3
(8.4)
0
(0)
0
(0)
0
(0)
0
(0)
0
(0)
0.1
(0.25)
2.9
(7.4)
7.4
(19)
46.2
(117)
Average precipitation days (≥ 0.01 in) 12.0 11.0 11.8 12.3 13.2 12.8 11.2 11.3 10.2 10.7 11.2 11.5 139.2
Average snowy days (≥ 0.1 in) 9.3 7.7 5.0 1.7 0 0 0 0 0 0.1 2.1 7.1 33.0
Average relative humidity (%) 70.1 67.5 63.3 60.4 64.6 70.5 71.1 73.8 75.2 71.6 71.8 72.5 69.4
Mean monthly sunshine hours 130.3 143.7 185.7 210.5 246.9 269.7 285.7 257.2 200.2 173.3 104.3 95.9 2,303.4
Percent possible sunshine 44 48 50 53 55 60 62 60 54 50 35 33 52
Source: NOAA (relative humidity 1964–1990, sun 1961–1990)
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