# Climate Design Data Workflow for Chicago, IL

> A source-first workflow for retrieving and recording building-design climate conditions for Chicago, IL without mixing climate normals, code zones, and HVAC design percentiles.

- Canonical: https://harth.build/resources/climate-data/climate-design-data-workflow-chicago-il/
- Last updated: 2026-08-31
- Data source: Licensed ASHRAE Climatic Design Information / Standard 169 station data plus the locally adopted energy code. Coordinates 41.8781° N (America/Chicago) are approximate routing references. Figures are illustrative — confirm the representative station and current edition. Climate screening data from the [NASA POWER Climatology API documentation](https://power.larc.nasa.gov/docs/services/api/temporal/climatology/) and [exact point response](https://power.larc.nasa.gov/api/temporal/climatology/point?parameters=T2M%2CT2M_MAX%2CT2M_MIN%2CRH2M%2CPRECTOTCORR%2CWS10M&community=SB&longitude=-87.6298&latitude=41.8781&format=JSON), retrieved 2026-08-31; source period: 20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020). NASA POWER values are gridded screening statistics, not code design conditions or guaranteed local observations.

## Key facts

| Fact | Value |
| --- | --- |
| NASA POWER climatology | 20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020) (API v2.9.7; LST) |
| Annual mean temperature | 9.8 °C (2 m gridded climatology; not a design percentile) |
| Highest monthly maximum | 34.7 °C (July) (monthly climatological statistic) |
| Lowest monthly minimum | -24.8 °C (January) (monthly climatological statistic) |
| Annual relative humidity | 80.8% (2 m gridded climatology) |
| Annual corrected precipitation | 2.69 mm/day (climatological daily rate) |
| Annual wind speed | 5.65 m/s (10 m gridded climatology; not a structural design wind speed) |

## Direct answer

NASA POWER's 2001–2020 climatology at the Chicago, IL reference point reports an annual mean 2 m temperature of 9.8 °C and relative humidity of 80.8%. The highest monthly maximum is 34.7 °C in July, while the lowest monthly minimum is -24.8 °C in January; these are screening statistics, not code design temperatures. The point response uses LST and the 20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020); its annual corrected precipitation is 2.69 mm/day and annual 10 m wind speed is 5.65 m/s. Use the monthly series to screen source selection before applying project design conditions. NASA POWER is gridded climatology: verify elevation, microclimate, urban exposure, station or weather-file suitability, current code edition and the authority's required source before design use.

*Content and cited inputs reviewed by [Harth team](https://www.linkedin.com/company/harth-build) · Published 2026-08-17 · Updated 2026-08-31.*

## Which climate inputs control the design?

1. Confirm the project jurisdiction and adopted energy-code edition.
2. Select the authoritative station and record why it applies.
3. Record heating dry-bulb percentiles and cooling dry-bulb with coincident moisture conditions.
4. Keep IP/SI units, edition, observation period and retrieval date with every value.
5. Separate climate-zone envelope requirements from HVAC sizing conditions.

| Field | Required record |
| --- | --- |
| Station | Name, ID, coordinates and elevation |
| Source | Publisher, edition and licensed/public status |
| Heating | 99.6% and 99% dry-bulb |
| Cooling | 0.4%, 1% and 2% dry-bulb plus coincident wet-bulb |
| Moisture | Dew-point or humidity design condition used |
| Code | Adopted edition, amendments and effective date |

## Chicago, IL NASA POWER monthly climate screening table

| Month | Mean °C | Monthly max °C | Monthly min °C | RH % | Precipitation mm/day | Wind at 10 m m/s |
| --- | ---: | ---: | ---: | ---: | ---: | ---: |
| January | -2.52 | 11.85 | -24.81 | 86.39 | 1.54 | 7.05 |
| February | -2.31 | 13.86 | -19.39 | 84.23 | 1.90 | 6.55 |
| March | 2.03 | 20.95 | -17.30 | 81.55 | 2.00 | 5.90 |
| April | 6.86 | 22.86 | -4.41 | 80.67 | 3.15 | 5.83 |
| May | 11.80 | 29.00 | 0.82 | 82.61 | 3.79 | 5.01 |
| June | 18.08 | 30.67 | 3.74 | 81.32 | 3.41 | 4.33 |
| July | 22.53 | 34.70 | 12.23 | 78.16 | 3.07 | 4.09 |
| August | 22.57 | 32.35 | 12.96 | 76.53 | 3.40 | 4.24 |
| September | 19.15 | 30.66 | 8.02 | 76.25 | 2.86 | 5.09 |
| October | 12.35 | 26.18 | 0.13 | 76.85 | 3.18 | 6.18 |
| November | 6.02 | 19.78 | -8.07 | 79.76 | 2.03 | 6.73 |
| December | 0.46 | 16.41 | -18.55 | 85.32 | 1.88 | 6.85 |

![Monthly mean, maximum and minimum air temperature for Climate Design Data Workflow for Chicago, IL](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/climate-data/climate-design-data-workflow-chicago-il/chart-temperature-1344.webp)

*Monthly air temperature for Climate Design Data Workflow for Chicago, IL, plotted from the table above.*

![Mean daily precipitation by month for Climate Design Data Workflow for Chicago, IL](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/climate-data/climate-design-data-workflow-chicago-il/chart-precipitation-1344.webp)

*Mean daily precipitation for Climate Design Data Workflow for Chicago, IL, plotted from the table above.*

## Month-by-month climate interpretation

- **January:** mean temperature -2.52 °C is 12.33 °C below the annual mean; the monthly max–min span is 36.66 °C. Relative humidity is 86.39% (5.60 points above annual), while corrected precipitation at 1.54 mm/day is 1.15 mm/day drier than the annual daily rate.
- **February:** mean temperature -2.31 °C is 12.12 °C below the annual mean; the monthly max–min span is 33.25 °C. Relative humidity is 84.23% (3.44 points above annual), while corrected precipitation at 1.90 mm/day is 0.79 mm/day drier than the annual daily rate.
- **March:** mean temperature 2.03 °C is 7.78 °C below the annual mean; the monthly max–min span is 38.25 °C. Relative humidity is 81.55% (0.76 points above annual), while corrected precipitation at 2.00 mm/day is 0.69 mm/day drier than the annual daily rate.
- **April:** mean temperature 6.86 °C is 2.95 °C below the annual mean; the monthly max–min span is 27.27 °C. Relative humidity is 80.67% (0.12 points below annual), while corrected precipitation at 3.15 mm/day is 0.46 mm/day wetter than the annual daily rate.
- **May:** mean temperature 11.80 °C is 1.99 °C above the annual mean; the monthly max–min span is 28.18 °C. Relative humidity is 82.61% (1.82 points above annual), while corrected precipitation at 3.79 mm/day is 1.10 mm/day wetter than the annual daily rate.
- **June:** mean temperature 18.08 °C is 8.27 °C above the annual mean; the monthly max–min span is 26.93 °C. Relative humidity is 81.32% (0.53 points above annual), while corrected precipitation at 3.41 mm/day is 0.72 mm/day wetter than the annual daily rate.
- **July:** mean temperature 22.53 °C is 12.72 °C above the annual mean; the monthly max–min span is 22.47 °C. Relative humidity is 78.16% (2.63 points below annual), while corrected precipitation at 3.07 mm/day is 0.38 mm/day wetter than the annual daily rate.
- **August:** mean temperature 22.57 °C is 12.76 °C above the annual mean; the monthly max–min span is 19.39 °C. Relative humidity is 76.53% (4.26 points below annual), while corrected precipitation at 3.40 mm/day is 0.71 mm/day wetter than the annual daily rate.
- **September:** mean temperature 19.15 °C is 9.34 °C above the annual mean; the monthly max–min span is 22.64 °C. Relative humidity is 76.25% (4.54 points below annual), while corrected precipitation at 2.86 mm/day is 0.17 mm/day wetter than the annual daily rate.
- **October:** mean temperature 12.35 °C is 2.54 °C above the annual mean; the monthly max–min span is 26.05 °C. Relative humidity is 76.85% (3.94 points below annual), while corrected precipitation at 3.18 mm/day is 0.49 mm/day wetter than the annual daily rate.
- **November:** mean temperature 6.02 °C is 3.79 °C below the annual mean; the monthly max–min span is 27.85 °C. Relative humidity is 79.76% (1.03 points below annual), while corrected precipitation at 2.03 mm/day is 0.66 mm/day drier than the annual daily rate.
- **December:** mean temperature 0.46 °C is 9.35 °C below the annual mean; the monthly max–min span is 34.96 °C. Relative humidity is 85.32% (4.53 points above annual), while corrected precipitation at 1.88 mm/day is 0.81 mm/day drier than the annual daily rate.

Harth retrieved this point climatology from NASA POWER API v2.9.7 for location record us:chicago-il. It is a reproducible screening dataset, not an hourly weather file, forecast, code design condition or substitute for local professional review.

## Where can you explore related guidance?

- [Explore all climate data guidance](https://harth.build/resources/climate-data.md)
- [ASHRAE / IECC Climate Zones Explained (Zones 1–8, A/B/C)](https://harth.build/resources/climate-data/ashrae-climate-zones-explained.md)
- [Heating & Cooling Design Temperatures (99%, 1% / 0.4%)](https://harth.build/resources/climate-data/heating-and-cooling-design-temperatures.md)
- [Climate Design Data Workflow for Nashville, TN](https://harth.build/resources/climate-data/climate-design-data-workflow-nashville-tn.md)
- [Climate Design Data Workflow for Minneapolis, MN](https://harth.build/resources/climate-data/climate-design-data-workflow-minneapolis-mn.md)
- [Sun Path & Solar Angles for Chicago, IL](https://harth.build/resources/solar-data/sun-path-and-solar-angles-chicago-il.md)

## Sources and method

Licensed ASHRAE Climatic Design Information / Standard 169 station data plus the locally adopted energy code. Coordinates 41.8781° N (America/Chicago) are approximate routing references. Figures are illustrative — confirm the representative station and current edition. Climate screening data from the [NASA POWER Climatology API documentation](https://power.larc.nasa.gov/docs/services/api/temporal/climatology/) and [exact point response](https://power.larc.nasa.gov/api/temporal/climatology/point?parameters=T2M%2CT2M_MAX%2CT2M_MIN%2CRH2M%2CPRECTOTCORR%2CWS10M&community=SB&longitude=-87.6298&latitude=41.8781&format=JSON), retrieved 2026-08-31; source period: 20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020). NASA POWER values are gridded screening statistics, not code design conditions or guaranteed local observations.

### Source links

- [power.larc.nasa.gov](https://power.larc.nasa.gov/docs/services/api/temporal/climatology/)

- [power.larc.nasa.gov](https://power.larc.nasa.gov/api/temporal/climatology/point?parameters=T2M%2CT2M_MAX%2CT2M_MIN%2CRH2M%2CPRECTOTCORR%2CWS10M&community=SB&longitude=-87.6298&latitude=41.8781&format=JSON)

## Frequently asked questions

### What does NASA POWER climatology show for Chicago, IL?

For the Chicago, IL reference point, the 2001–2020 NASA POWER climatology reports 9.8 °C annual mean temperature, 80.8% relative humidity and 2.69 mm/day corrected precipitation. The monthly maximum peaks at 34.7 °C in July.

### Can the Chicago, IL climatology replace project design temperatures or an hourly weather file?

No. The Chicago, IL response is gridded monthly climatology; its lowest monthly minimum of -24.8 °C in January is not a code percentile or observed site extreme. Verify elevation, local exposure, the required weather file or design-condition source and the current adopted code.

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