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Typical weather at station CHICAGO O'HARE INTERNATIONAL on September 21

High Temperatures

On September 21 in CHICAGO O'HARE INTERNATIONAL the average high temperature is 74.8 °F (23.8 °C). The lowest recored high temperature was 53.1 °F (11.7 °C) in 1983 and the highest recored high temperature was 93.9 °F (34.4 °C) in 2017. The high temperature is usually* between 68.8 °F (20.4 °C) and 80.8 °F (27.1 °C). About a quarter of the time, the high temperature is less than 68.8 °F (20.4 °C), and another quarter of the time, the high temperature is greater than and 80.8 °F (27.1 °C). About 95% of the time, the high temperature has been between 57.3 °F (14.0 °C) and 92.4 °F (33.5 °C).

Low Temperatures

On September 21 in CHICAGO O'HARE INTERNATIONAL the average low temperature is 53.5 °F (11.9 °C). The lowest recored low temperature was 33.1 °F (0.6 °C) in 1962 and the lowest recored low temperature was 73.0 °F (22.8 °C) in 1970. The low temperature is usually* between 47.8 °F (8.8 °C) and 59.2 °F (15.1 °C). About a quarter of the time, the low temperature is less than 47.8 °F (8.8 °C), and another quarter of the time, the low temperature is greater than and 59.2 °F (15.1 °C). About 95% of the time, the low temperature has been between 36.9 °F (2.7 °C) and 70.1 °F (21.2 °C).

Frost

On September 21 in CHICAGO O'HARE INTERNATIONAL expect the temperatures to drop below freezing for a risk of frost about 0.6% of the time.

Usually* in this context means around 50% of the time, assuming a normal distribution of values.

Data Source(s)

The data used to compute the average high/low temperatures for this location were taken from the following stations: