Station information
- Integrated Surface Dataset (ISD) station ID: 998499
- Country: US
- State: IL
- Latitude: 41.856
- Longitude: -87.609
High Temperatures
On May 21 in NORTHERLY ISLAND the average high temperature is 71.8 °F (22.1 °C). The lowest recored high temperature was 54.0 °F (12.2 °C) in 2025 and the highest recored high temperature was 87.4 °F (30.8 °C) in 2024. The high temperature is usually* between 63.2 °F (17.4 °C) and 80.3 °F (26.9 °C). About a quarter of the time, the high temperature is less than 63.2 °F (17.4 °C), and another quarter of the time, the high temperature is greater than and 80.3 °F (26.9 °C). About 95% of the time, the high temperature has been between 47.0 °F (8.3 °C) and 96.6 °F (35.9 °C).
Low Temperatures
On May 21 in NORTHERLY ISLAND the average low temperature is 51.5 °F (10.8 °C). The lowest recored low temperature was 41.0 °F (5.0 °C) in 2015 and the lowest recored low temperature was 65.1 °F (18.4 °C) in 2013. The low temperature is usually* between 47.0 °F (8.4 °C) and 55.9 °F (13.3 °C). About a quarter of the time, the low temperature is less than 47.0 °F (8.4 °C), and another quarter of the time, the low temperature is greater than and 55.9 °F (13.3 °C). About 95% of the time, the low temperature has been between 38.6 °F (3.7 °C) and 64.4 °F (18.0 °C).
Frost
On May 21 in NORTHERLY ISLAND expect the temperatures to drop below freezing for a risk of frost about 0.2% of the time.
Data Source(s)
The data used to compute the average high/low temperatures for this location were taken from the following stations:
- NORTHERLY ISLAND — Integrated Surface Dataset (ISD) station ID: 998499 — from year 2013 to 2025