Home / United States / Grayslake
Grayslake climate
Typical historical weather for Grayslake, United States, averaged across 10 years of hourly climate data. Pick a date for a specific day.
Want today's actual conditions instead? See the current forecast for Grayslake. Planning a garden? See the gardening & growing season planner. Or browse the 365-day climate calendar.
Annual average
10.3°C
across all months
Warmest month
26.4°C
Jul average high
Coolest month
-6.3°C
Jan average low
Annual rainfall
1024mm
total per year
Grayslake is typically hottest in July and coolest in January, a swing of about 32.7°C across the year. About 33% of annual rainfall falls in the three wettest months (May is typically wettest, February driest).
Monthly averages
Average daily high/low temperature (band) and monthly rainfall (bars).
| Month | Avg high | Avg low | Rainfall | Wet days | Humidity | Wind | Cloud | Solar |
|---|---|---|---|---|---|---|---|---|
| Jan | -0.5°C · record 3.9–12.5°C | -6.3°C · record -29.7–-14.4°C | 69mm | 10 | 74% | 4.6 m/s | 74% | 1.8 kWh/m² |
| Feb | 2°C · record 8.1–20°C | -5.2°C · record -21.4–-10.7°C | 57mm | 9 | 69% | 4.7 m/s | 65% | 2.9 kWh/m² |
| Mar | 7.3°C · record 11.5–22.3°C | 0.3°C · record -20.3–-3.3°C | 91mm | 12 | 69% | 4.5 m/s | 66% | 3.9 kWh/m² |
| Apr | 11.9°C · record 21.6–25.3°C | 4.3°C · record -6.7–1.3°C | 117mm | 13 | 67% | 4.4 m/s | 65% | 5 kWh/m² |
| May | 17.7°C · record 25.3–29.3°C | 10.2°C · record 0.2–8.2°C | 121mm | 13 | 70% | 3.8 m/s | 63% | 5.9 kWh/m² |
| Jun | 24.1°C · record 27.2–33.3°C | 16.4°C · record 6.8–11.8°C | 92mm | 12 | 71% | 3.5 m/s | 54% | 6.6 kWh/m² |
| Jul | 26.4°C · record 29.3–33°C | 19.5°C · record 12.7–17.7°C | 92mm | 12 | 75% | 3 m/s | 53% | 6.4 kWh/m² |
| Aug | 25.9°C · record 27.6–34.9°C | 18.9°C · record 12.4–15.2°C | 81mm | 11 | 75% | 3.1 m/s | 50% | 5.6 kWh/m² |
| Sep | 23.2°C · record 28.7–32.3°C | 15.8°C · record 5.4–12.8°C | 77mm | 10 | 74% | 3.6 m/s | 49% | 4.5 kWh/m² |
| Oct | 16.3°C · record 23.6–29.3°C | 9.1°C · record -0.9–5.1°C | 105mm | 11 | 71% | 4.4 m/s | 56% | 3 kWh/m² |
| Nov | 8.5°C · record 11.5–22.5°C | 2°C · record -12.9–-2.3°C | 59mm | 8 | 70% | 4.7 m/s | 61% | 2.1 kWh/m² |
| Dec | 2.7°C · record 9.7–17.9°C | -3°C · record -22.1–-7.1°C | 62mm | 9 | 73% | 4.6 m/s | 71% | 1.6 kWh/m² |
"Avg high"/"Avg low" is the mean daily high/low for that month, averaged across every year on file. The "record" figure alongside it is a different statistic — the single hottest (or coldest) hour ever recorded during that month across all years — so it can sit above or below the average and does not describe the average's year-to-year spread. A "wet day" is any day with at least 1.0mm of rain.
Year to year
Annual average temperature, 2016–2025.
Across these 10 years, the annual average has moved by about +0.81°C per decade. That’s a short window for a reliable long-term climate trend — treat it as indicative, not definitive.
Annual rainfall has moved by about -296.25mm per decade over the same period.
2025 (the most recent year on file) averaged 10.144333037284976°C, below the 9-year baseline of 10.37°C by 0.31 standard deviations.
Typical extremes per year
Rainy days
128.2 days
≥1.0mm rain
Heavy rain days
10.2 days
≥20mm rain
Extreme heat days
0 days
daily high ≥40°C
Frost days
96.2 days
daily low ≤0°C
Averaged across 10 years on file. Thresholds match PastClimate's data pipeline definitions — see data & sources.
Records on file
Ranked across 10 years of data currently on file (2016–2025).
Hottest day
34.9°C
23 August 2023
2023 was 0.99 SD above the 9-year average that year
Coldest day
-29.7°C
31 January 2019
2019 was 2.27 SD below the 9-year average that year
Wettest day
68.7mm
17 May 2020
2020 was 0.14 SD above the 9-year average that year
Windiest day
10.5m/s
26 November 2025
2025 was 0.31 SD below the 9-year average that year
See the detail: Grayslake on 17 May 2020.
Nearby cities
Buffalo Grove
Same ERA5 grid cell
Wheeling
Same ERA5 grid cell
Mundelein
Same ERA5 grid cell
Gurnee
Same ERA5 grid cell
Round Lake Beach
Same ERA5 grid cell
Vernon Hills
Same ERA5 grid cell
Want a side-by-side view instead? Compare Grayslake with another city.
Frequently asked questions about Grayslake's climate
What is the hottest month in Grayslake?
July is typically the warmest month in Grayslake, with an average high of 26.4°C. January is typically the coolest, averaging -6.3°C overnight.
How much does it rain in Grayslake?
Grayslake gets about 1024mm of rain a year on average, with roughly 33% of it falling in the three wettest months (May is typically the wettest, February the driest).
How many extremely hot or cold days does Grayslake have?
On average, Grayslake sees about 0 day(s) a year at or above 40°C and about 96.2 day(s) at or below 0°C, based on 10 years of data.
Is Grayslake getting warmer?
Across the 10 years on file (2016–2025), the annual average temperature has moved by about +0.81°C per decade. That's a short window for a reliable long-term climate trend — treat it as indicative, not definitive.
What is the hottest day on record for Grayslake?
The hottest day on file is 23 August 2023 at 34.9°C, out of 10 year(s) searched.
Data & provenance
↓ Download monthly CSVData source & coverage — ERA5 reanalysis, 2016–2025 (10 years)details
- Source
- ERA5 reanalysis, accessed via the Copernicus Climate Change Service (C3S) Climate Data Store
- Data type
- Reanalysis — a physically consistent reconstruction combining a forecast model with historical observations, not a live station reading or a forecast
- Coverage
- 2016–2025 (10 years) for United States
- Location
- Grayslake — 42.250°, -88.000°, ERA5 grid cell center, 11.1 km from requested point
- Time zone
- America/Chicago
- What's shown here
- Monthly and annual averages, and dated extreme-value records, derived from an hourly base record.
- Spatial resolution
- 0.25° (~25 km) distributed grid — ERA5's native model resolution is finer; this is the publicly distributed regridded product
- Version / refreshed
- Methodology v2026.07 · data last refreshed December 31, 2025
- Limitations
- A model reconstruction, not a station observation — hyper-local extremes (a single storm cell, an urban heat pocket) can differ from a nearby gauge. See the full methodology.
- Attribution
- Generated using Copernicus Climate Change Service information
Cite this data
PastClimate (2026-07-18). Historical climate data for Grayslake, United States (42.25°N, 88.00°W), derived from ERA5 (Hersbach et al., 2023, Copernicus Climate Change Service). Retrieved from https://www.pastclimate.com/
PastClimate. (2026). Historical climate data for Grayslake, United States [Data set]. Derived from ERA5 (Copernicus Climate Change Service). Retrieved July 18, 2026, from https://www.pastclimate.com/
"Historical Climate Data for Grayslake, United States." PastClimate, derived from ERA5 (Copernicus Climate Change Service), July 18, 2026, www.pastclimate.com.
@misc{pastclimate,
author = {PastClimate},
title = {Historical climate data for Grayslake, United States},
year = {2026},
note = {Derived from ERA5 (Hersbach et al., 2023), Copernicus Climate Change Service. Accessed 2026-07-18},
url = {https://www.pastclimate.com/}
}Notice something wrong with this data? Report a data issue.