Climate of Allentown, Pennsylvania
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The climate of Allentown, Pennsylvania is classified as being in the transition between a humid continental and humid subtropical climate (Köppen Dfa/Cfa, respectively), although lying closer to the former. Allentown's warmest month (on average) is July with a daily average temperature of 73.4 °F (23.0 °C) and the coldest month (on average) being January with a daily average of 27.8 °F (−2.3 °C). The average precipitation of Allentown is 45.35 inches (1,152 mm) per year. Allentown occasionally has some severe weather, mostly thunderstorms and flooding. Winters can bring snow, with some years receiving very little of it while others seeing several major snowstorms (often Nor'easters). Winter also brings the more dangerous ice, sleet, and freezing rain, which has caused several traffic accidents over the years. Tropical storms and hurricanes occasionally survive up the coast of the Atlantic Ocean and cross into Pennsylvania. Storms such as Hurricane Ivan and more recently Hurricane Sandy have caused light to severe damage in the area.
Average temperatures
| Climate data for Allentown, Pennsylvania (Lehigh Valley Int'l), 1981–2010 normals,[lower-alpha 1] extremes 1922–present[lower-alpha 2] | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 72 (22) |
76 (24) |
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) |
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) |
| Average high °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) |
82.4 (28) |
74.9 (23.8) |
63.6 (17.6) |
52.5 (11.4) |
40.5 (4.7) |
61.4 (16.3) |
| Average low °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) |
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 (68.6) |
3.39 (86.1) |
3.56 (90.4) |
4.14 (105.2) |
4.31 (109.5) |
4.95 (125.7) |
3.69 (93.7) |
4.62 (117.3) |
3.88 (98.6) |
3.50 (88.9) |
3.58 (90.9) |
45.35 (1,151.9) |
| Average snowfall inches (cm) | 10.0 (25.4) |
11.1 (28.2) |
4.9 (12.4) |
1.0 (2.5) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0 (0) |
0.7 (1.8) |
5.2 (13.2) |
32.9 (83.6) |
| 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 | .4 | 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)[1][2] | |||||||||||||
Extremes
All records date back to 1922:[1]
Temperature
- Highest recorded temperature: 105 °F (41 °C) on July 3, 1966
- Lowest daily maximum temperature: 2 °F (−17 °C) on January 19, 1994
- Highest daily minimum temperature: 79 °F (26 °C) on July 15, 1995
- Lowest recorded temperature: −15 °F (−26 °C) on January 21, 1994
- Highest daily average temperature: 91.0 °F (32.8 °C) on July 22, 2011
- Lowest daily average temperature: −4.5 °F (−20.3 °C) on January 19, 1994
Precipitation and snow
- Most precipitation in 24 hours: 8.71 in (221.2 mm)
- Heaviest 24-hour snowfall: 24.0 in (61.0 cm) on February 11, 1983.
- Greatest daily snow depth: 28 in (71 cm) on February 12, 1983.
Summer
Summers in Eastern Pennsylvania are hot and very humid, with temperatures in the mid-80s and low-90s. The average high temperature peaks at 84 °F (29 °C), but highs can often surpass that, with the all-time record high standing at 105 °F (41 °C). Humidity is often around 80 percent, which is a drastic change for someone living in the Southwest United States. Rain is common, and is often accompanied by strong or severe thunderstorms. These will cause quite a large amount of rain, but they do not last long at all. Air conditioning is popular among most households in the summer months, because high temperatures and high humidity can make the air feel much warmer than the actual temperature.
Autumn
Autumn is fairly mild, with daytime temperatures in the 70s and 60s. Autumn brings more wind, and sometimes heavier rainfall. Trees begin to lose their leaves before the cold winter season. Indian summer may occur.
Winter
Winters are cool to cold, with January's high temperature at 35 °F (2 °C). The highest temperature recorded was 76 °F (24 °C) in February, 87 °F (31 °C) in March, and 72 °F (22 °C) in both December and January. Snowfall is common, with amounts varying greatly between seasons. Snow, ice, sleet, and freezing rain can cause road problems and school closures. A couple years ago in February, I-78 was closed just west of the city. Drivers were stranded on the stretch of highway for as much as 18 hours, with overturned tractor trailers blocking the way. Winter sports are popular, such as snowboarding and skiing, and they can be enjoyed in the Pocono Mountains, just north of the Lehigh Valley.
Spring
Spring is a season of growth, with new grass growing and flowers blooming. Animals come out of hibernation, and sun fills the city and its surroundings. Temperatures are on the rise, but March and April bring much rain, with light rain that can last for hours on end. That gives way to warm May and June months, and shore weather is in the forecast for many residents.
Natural disasters
Hurricanes, Tropical storms, and Tropical Depressions are all summer threats. Severe thunderstorms are an even bigger threat, and can cause flash flooding. When flash flooding occurs, mudslides are rare but are possible. Tornadoes and earthquakes are not common, but they have been reported. Blizzards have happened, but usually once every ten or fifteen years.
Pollution
Air pollution is a problem in the area, as with Philadelphia and New York City, both of which lie less than 100 miles from Allentown. Although many factories have left, air pollution is still a problem. Light pollution is becoming an issue, since streetlights and businesses are on every street in the city. Water pollution is a problem in some of the creeks because of illegal dumping, but the city's water and sewer system keeps the Lehigh River and Delaware River clean.
See also
Notes
- ↑ Mean monthly maxima and minima (i.e. the highest and lowest temperature readings during an entire month or year) calculated based on data at said location from 1981 to 2010.
- ↑ Official records for Allentown were kept at Allentown Gas Company from March 1922 to December 1943, and at Lehigh Valley Int'l since January 1944. For more information, see ThreadEx.
References
- 1 2 "NowData - NOAA Online Weather Data". National Oceanic and Atmospheric Administration. Retrieved 2016-04-13.
- ↑ "WMO Climate Normals for ALLENTOWN/A.-BETHLEHEM, PA 1961–1990". National Oceanic and Atmospheric Administration. Retrieved 2014-05-28.