Climate - Allentown (Pennsylvania)

The climate of Allentown is continental, with very cold winters and warm to hot summers, during which there are quite frequent thunderstorms.
The city is located in the eastern United States, in eastern Pennsylvania, along the Lehigh River. The nearby cities of Bethlehem and Easton are part of the metropolitan area.
The average temperature of the coldest month (January) is of -1.1 °C (30 °F), that of the warmest month (July) is of 24.2 °C (76 °F). Here are the average temperatures.

Precipitation amounts to 1,205 millimeters (47.4 inches) per year: it is therefore quite abundant. It ranges from 70 mm (2.8 in) in the driest month (February) to 135 mm (5.3 in) in the wettest (July). Here is the average precipitation.

Winter, from late November to early March, is very cold. Snowfalls are frequent, and at times can be abundant. On average, 84 centimeters (33 inches) of snow fall per year.
Cold waves are intense, in fact, the temperature typically drops to -15 °C (5 °F) on the coldest nights of the year, and can drop to -20 °C (-4 °F) once every few years. The record cold, -26 °C (-15 °F), was set in January 1994.
However, there can also be short, fairly mild periods, with highs of 12/13 °C (54/55 °F) or more.

Summer, from June to August, is hot and quite sunny, although thunderstorms can break out in the afternoon.
However, there can sometimes be very hot and muggy periods. Typically, the temperature reaches 35/36 °C (95/97 °F) on the hottest days of the year, although the record is 40 °C (104 °F), set in July 2011.

Spring and autumn, from mid-March to May and from September to mid-November, are contrasted seasons, with fairly frequent rains and sudden changes in temperature. However, there are also stable and pleasant periods.

Best Time

The best times to visit Allentown are spring and autumn, especially the months of May and September.
In October, typically peaking in the second and third week, you can admire the beautiful colors of the trees losing their leaves (the phenomenon called fall foliage).

Allentown - Weather by month

Based on the period 1991-2020

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In January, the coldest month of the year, the weather in Allentown is usually very cold. The average temperature is of -1.1 °C (30 °F), with a minimum of -5.7 °C (21.8 °F) and a maximum of 3.6 °C (38.4 °F).
On the coldest nights of the month, the temperature usually drops to around -15.5 °C (4.5 °F). However, it dropped to -26.2 °C (-15.2 °F) in January 1994.
On the warmest days of the month, the temperature usually reaches around 15.5 °C (60 °F). However, it reached 21.1 °C (70 °F) in January 2007.
Precipitation amounts to 85 mm (3.3 in), distributed over 11 days.
The day lasts on average 9 hours and 40 minutes.
The average humidity is 66%.
The average wind speed is 13 kph (8 mph).

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In February, the weather in Allentown is usually cold. The average temperature is of 0.2 °C (32 °F), with a minimum of -4.9 °C (23.2 °F) and a maximum of 5.3 °C (41.6 °F).
On the coldest nights of the month, the temperature usually drops to around -14.5 °C (6.5 °F). However, it dropped to -22.2 °C (-8 °F) in February 1996.
On the warmest days of the month, the temperature usually reaches around 15.5 °C (60.5 °F). However, it reached 27.2 °C (81 °F) in February 2018.
Precipitation amounts to 70 mm (2.8 in), distributed over 10 days.
The day lasts on average 10 hours and 40 minutes.
The average humidity is 62%.
The average wind speed is 13 kph (8 mph).

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In March, the weather in Allentown is usually quite cold. The average temperature is of 4.8 °C (41 °F), with a minimum of -0.8 °C (30.5 °F) and a maximum of 10.4 °C (50.8 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -10 °C (14 °F). However, it dropped to -17.8 °C (0 °F) in March 2015.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 21.5 °C (70.5 °F). However, it reached 30.6 °C (87.1 °F) in March 1998.
Precipitation amounts to 90 mm (3.5 in), distributed over 11 days.
The day lasts on average 12 hours and 0 minutes.
The average humidity is 59%.
The average wind speed is 14 kph (9 mph).

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In April, the weather in Allentown is usually mild. The average temperature is of 11.0 °C (52 °F), with a minimum of 4.6 °C (40.3 °F) and a maximum of 17.4 °C (63.4 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -3.5 °C (26 °F). However, it dropped to -6.7 °C (19.9 °F) in April 2016.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 28.5 °C (83.5 °F). However, it reached 33.3 °C (91.9 °F) in April 2010.
Precipitation amounts to 95 mm (3.7 in), distributed over 12 days.
The day lasts on average 13 hours and 25 minutes.
The average humidity is 57%.
The average wind speed is 14 kph (8 mph).

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In May, the weather in Allentown is usually very mild. The average temperature is of 16.7 °C (62 °F), with a minimum of 10.3 °C (50.6 °F) and a maximum of 23.1 °C (73.5 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 2 °C (35.5 °F). However, it dropped to -1.7 °C (28.9 °F) in May 1996.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 32 °C (89.5 °F). However, it reached 34.4 °C (93.9 °F) in May 2013.
Precipitation amounts to 95 mm (3.7 in), distributed over 12 days.
The day lasts on average 14 hours and 30 minutes. So the days are long.
The average humidity is 63%.
The average wind speed is 11 kph (7 mph).

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In June, the weather in Allentown is usually warm. The average temperature is of 21.6 °C (71 °F), with a minimum of 15.5 °C (59.9 °F) and a maximum of 27.7 °C (81.9 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 8 °C (46 °F). However, it dropped to 2.8 °C (37 °F) in June 1996.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 33.5 °C (92.5 °F). However, it reached 36.1 °C (97 °F) in June 1991.
Precipitation amounts to 110 mm (4.3 in), distributed over 11 days.
The day lasts on average 15 hours and 0 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
The average humidity is 67%.
The average wind speed is 11 kph (7 mph).

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In July, the warmest month of the year, the weather in Allentown is usually warm to hot. The average temperature is of 24.2 °C (76 °F), with a minimum of 18.2 °C (64.7 °F) and a maximum of 30.2 °C (86.4 °F).
On the coldest nights of the month, the temperature usually drops to around 12 °C (54 °F). However, it dropped to 7.8 °C (46 °F) in July 2001.
On the warmest days of the month, the temperature usually reaches around 35 °C (95 °F). However, it reached 40 °C (104 °F) in July 2011.
Precipitation amounts to 135 mm (5.3 in), distributed over 11 days.
The day lasts on average 14 hours and 40 minutes. So the days are long.
The average humidity is 68%.
The average wind speed is 10 kph (6 mph).

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In August, the weather in Allentown is usually warm to hot and muggy. The average temperature is of 23.1 °C (74 °F), with a minimum of 17.1 °C (62.8 °F) and a maximum of 29.1 °C (84.3 °F).
On the coldest nights of the month, the temperature usually drops to around 10.5 °C (51.5 °F). However, it dropped to 7.2 °C (45 °F) in August 2000.
On the warmest days of the month, the temperature usually reaches around 33.5 °C (92.5 °F). However, it reached 37.2 °C (99 °F) in August 1999.
Precipitation amounts to 115 mm (4.5 in), distributed over 10 days.
The day lasts on average 13 hours and 40 minutes.
The average humidity is 70%. Hence, the air is normally humid.
The average wind speed is 9 kph (5 mph).

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In September, the weather in Allentown is usually warm. The average temperature is of 19.1 °C (66 °F), with a minimum of 12.9 °C (55.2 °F) and a maximum of 25.2 °C (77.4 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 4.5 °C (40 °F). However, it dropped to 0 °C (32 °F) in September 2000.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 32 °C (89.5 °F). However, it reached 35.6 °C (96.1 °F) in September 2010.
Precipitation amounts to 125 mm (4.9 in), distributed over 10 days.
The day lasts on average 12 hours and 25 minutes.
The average humidity is 71%. Hence, the air is normally humid.
The average wind speed is 9 kph (6 mph).

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In October, the weather in Allentown is usually mild. The average temperature is of 12.6 °C (55 °F), with a minimum of 6.6 °C (43.8 °F) and a maximum of 18.6 °C (65.5 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -2 °C (29 °F). However, it dropped to -4.4 °C (24.1 °F) in October 2001.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 27 °C (80.5 °F). However, it reached 33.3 °C (91.9 °F) in October 2019.
Precipitation amounts to 105 mm (4.1 in), distributed over 10 days.
The day lasts on average 11 hours and 5 minutes.
The average humidity is 70%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).

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In November, the weather in Allentown is usually quite mild. The average temperature is of 6.6 °C (44 °F), with a minimum of 1.2 °C (34.1 °F) and a maximum of 12.1 °C (53.8 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -7 °C (19.5 °F). However, it dropped to -11.7 °C (10.9 °F) in November 2018.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 22 °C (71.5 °F). However, it reached 26.1 °C (79 °F) in November 1994.
Precipitation amounts to 80 mm (3.1 in), distributed over 9 days.
The day lasts on average 9 hours and 55 minutes.
The average humidity is 67%.
The average wind speed is 11 kph (7 mph).

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In December, the weather in Allentown is usually cold. The average temperature is of 1.6 °C (35 °F), with a minimum of -2.9 °C (26.8 °F) and a maximum of 6.2 °C (43.1 °F).
On the coldest nights of the month, the temperature usually drops to around -11 °C (12 °F). However, it dropped to -18.9 °C (-2 °F) in December 2005.
On the warmest days of the month, the temperature usually reaches around 16.5 °C (62 °F). However, it reached 22.2 °C (72 °F) in December 1998.
Precipitation amounts to 100 mm (3.9 in), distributed over 12 days.
The day lasts on average 9 hours and 20 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
The average humidity is 69%.
The average wind speed is 12 kph (7 mph).