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Chicago vs San Diego weather: climate comparison
San Diego is the warmer of the two, averaging 63°F (17°C) over the year against 50°F (10°C) in Chicago. Chicago is wetter, with 38.7 in (982 mm) of precipitation a year to San Diego's 11.7 in (298 mm). Below: every month side by side, from 30 years of ERA5 data (1996–2025).
- Mean temperature
- 10.1°C Chicago
17.0°C San Diego - Annual precipitation
- 982.3 mm Chicago
298.4 mm San Diego - Rainy days a year
- 121 Chicago
38 San Diego - Sunshine per day
- 8.8 h Chicago
10.9 h San Diego
Month by month
| Month | Chicago | San Diego |
|---|---|---|
| January | -0.9°C | 17.5°C |
| February | 0.6°C | 17.3°C |
| March | 5.4°C | 17.8°C |
| April | 11.4°C | 19.1°C |
| May | 17.9°C | 20.2°C |
| June | 24.2°C | 21.9°C |
| July | 26.6°C | 24.3°C |
| August | 25.8°C | 25.3°C |
| September | 22.5°C | 25.0°C |
| October | 15.6°C | 23.1°C |
| November | 8.3°C | 20.4°C |
| December | 2.2°C | 17.5°C |
Year at a glance
| Measure | Chicago | San Diego |
|---|---|---|
| Mean annual temperature | 10.1°C | 17.0°C |
| Warmest month (avg high) | Jul · 27°C | Aug · 25°C |
| Coldest month (avg low) | Jan · -7°C | Jan · 9°C |
| Annual range (warmest high − coldest low) | 34°C | 17°C |
| Annual precipitation | 982.3 mm | 298.4 mm |
| Rainy days per year | 121 | 38 |
| Wettest / driest month | May / Feb | Feb / Jun |
| Average sunshine per day | 8.8 h | 10.9 h |
In short: San Diego is the warmest overall (17.0°C mean); Chicago gets the most precipitation (982.3 mm a year); San Diego is the sunniest (10.9 h a day on average); San Diego has the smallest swing between its warmest and coldest months.
Record high 1996–2025: Chicago 37.4°C (2022-06-21), San Diego 36.6°C (2020-09-30). Record low: Chicago -32.5°C (2019-01-31), San Diego 1.8°C (2007-01-15).
Source: Open-Meteo Historical Weather API (CC BY 4.0). Values are ERA5 reanalysis model data on a ~9–25 km grid, not readings from a weather station, so a single town’s thermometer can differ by a few degrees and local showers can be missed. Monthly means of daily ERA5 values, 1996–2025, for the grid cells nearest Chicago (41.86, -87.65) and San Diego (32.72, -117.14).
Which months differ most?
The gap in average highs is widest in January, when San Diego runs 33°F / 18°C warmer, and narrowest in August (1°F / 1°C apart). The biggest rainfall difference is in May: Chicago gets 4.0 in (101 mm) more on average.
Add a third or fourth city, or swap in any other place, in the full comparison tool. For one city in depth, see the Chicago climate and San Diego climate pages.
Compare Chicago or San Diego with another city
Questions people ask
Is Chicago warmer than San Diego?
San Diego is warmer on average: its mean annual temperature is 63°F (17°C) against 50°F (10°C) in Chicago (ERA5, 1996–2025).
Which gets more rain, Chicago or San Diego?
Chicago, with about 38.7 in (982 mm) of precipitation a year and 121 days with at least 1 mm, compared with 11.7 in (298 mm) and 38 days in San Diego.
Which is sunnier, Chicago or San Diego?
San Diego averages more sunshine: 10.9 h a day against 8.8 h. Sunshine duration is modelled from cloud cover.
How reliable is this comparison?
Both cities use the same 30-year reanalysis, so differences are consistent. Absolute values describe a grid cell several kilometres wide and can differ by a degree or two from the airport station.