# Climate Design Data: Johannesburg, South Africa

> How to research climate design data for a specific site in Johannesburg — the controlling authority, source documents, and checks to run before you rely on a number.

- Canonical: https://harth.build/resources/climate-data/climate-design-data-johannesburg-za/
- Last updated: 2026-08-31
- Data source: Location data from the [GeoNames ZA dump](https://download.geonames.org/export/dump/ZA.zip) (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 993800). Regulatory starting point: [South African Bureau of Standards and the local authority](https://www.sabs.co.za/). Figures are illustrative — verify against the current locally adopted edition for the site. 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=28.04363&latitude=-26.20227&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 | 17.1 °C (2 m gridded climatology; not a design percentile) |
| Highest monthly maximum | 38.8 °C (January) (monthly climatological statistic) |
| Lowest monthly minimum | -4.8 °C (June) (monthly climatological statistic) |
| Annual relative humidity | 55.2% (2 m gridded climatology) |
| Annual corrected precipitation | 1.76 mm/day (climatological daily rate) |
| Annual wind speed | 3.48 m/s (10 m gridded climatology; not a structural design wind speed) |

## Direct answer

NASA POWER's 2001–2020 climatology at the Johannesburg reference point reports an annual mean 2 m temperature of 17.1 °C and relative humidity of 55.2%. The highest monthly maximum is 38.8 °C in January, while the lowest monthly minimum is -4.8 °C in June; 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 1.76 mm/day and annual 10 m wind speed is 3.48 m/s. For climate design data, use the 38.8 °C and -4.8 °C monthly extrema to screen seasonal exposure, then obtain the adopted percentile 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 2026-08-26 · Updated 2026-08-31.*

## What are the key takeaways?

- NASA POWER climatology: 20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020)
- Annual mean temperature: 17.1 °C
- Highest monthly maximum: 38.8 °C (January)
- Lowest monthly minimum: -4.8 °C (June)

## What must be verified for Johannesburg?

Johannesburg is represented here at approximately **-26.2023, 28.0436** for discovery and workflow planning. A project address, parcel, elevation, exposure, authority, and submission date must replace that city-centre reference before design use.

## How should climate design data be established?

1. Fix the surveyed site and local time basis.
2. Select an authoritative weather source or a named solar-position algorithm.
3. Record period, percentile or scenario and units.
4. Test sensitivity to elevation, exposure, urban form and horizon.
5. Save the source file, retrieval date and checker in the model record.

| Input | Project-specific evidence | QA question |
| --- | --- | --- |
| Site | surveyed coordinates, elevation and horizon | Does the point represent the building? |
| Weather/solar method | named dataset, algorithm, period and time basis | Are station, time zone and units explicit? |
| Design scenario | current and future scenario agreed by the team | Is an average being mistaken for an extreme? |
| Compliance | adopted local document and edition | Was applicability confirmed with the authority? |

## What are the limits of this worksheet?

This climate-design-workflow page is a project-starting worksheet, not a design value or approval. The controlling authority and qualified professionals for the Johannesburg site remain authoritative.

## Which related searches does this primary location record cover?

This primary route consolidates the location evidence needed for **Climate Design Data**, **Weather File Guide**, **Overheating Weather Data**, **Building Climate Checklist**. A narrower route should be released only when it adds a materially different official source, calculation, process, threshold or worked example.

## Johannesburg 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 | 21.64 | 38.75 | 6.96 | 65.13 | 3.95 | 3.04 |
| February | 21.38 | 35.13 | 8.79 | 64.06 | 2.90 | 2.89 |
| March | 19.86 | 33.83 | 6.12 | 63.04 | 2.36 | 2.87 |
| April | 16.67 | 31.36 | 1.04 | 62.21 | 1.44 | 2.97 |
| May | 13.32 | 29.31 | -4.20 | 54.12 | 0.51 | 3.14 |
| June | 10.03 | 25.41 | -4.75 | 54.65 | 0.23 | 3.50 |
| July | 9.89 | 25.81 | -4.00 | 49.19 | 0.09 | 3.53 |
| August | 13.08 | 29.79 | -4.20 | 43.61 | 0.23 | 4.11 |
| September | 17.34 | 33.39 | -1.47 | 38.95 | 0.53 | 4.26 |
| October | 19.91 | 36.69 | 2.92 | 48.19 | 1.83 | 4.16 |
| November | 20.72 | 36.89 | 4.97 | 56.51 | 2.97 | 3.88 |
| December | 21.45 | 36.52 | 6.51 | 63.34 | 4.09 | 3.36 |

![Monthly mean, maximum and minimum air temperature for Johannesburg, South Africa](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/climate-data/climate-design-data-johannesburg-za/chart-temperature-1344.webp)

*Monthly air temperature for Johannesburg, South Africa, plotted from the table above.*

![Mean daily precipitation by month for Johannesburg, South Africa](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/climate-data/climate-design-data-johannesburg-za/chart-precipitation-1344.webp)

*Mean daily precipitation for Johannesburg, South Africa, plotted from the table above.*

## Johannesburg ranked monthly climate fingerprint

- **Johannesburg mean temperature, highest to lowest:** January 21.64 °C, December 21.45 °C, February 21.38 °C, November 20.72 °C, October 19.91 °C, March 19.86 °C, September 17.34 °C, April 16.67 °C, May 13.32 °C, August 13.08 °C, June 10.03 °C, July 9.89 °C.
- **Johannesburg monthly maximum, highest to lowest:** January 38.75 °C, November 36.89 °C, October 36.69 °C, December 36.52 °C, February 35.13 °C, March 33.83 °C, September 33.39 °C, April 31.36 °C, August 29.79 °C, May 29.31 °C, July 25.81 °C, June 25.41 °C.
- **Johannesburg monthly minimum, highest to lowest:** February 8.79 °C, January 6.96 °C, December 6.51 °C, March 6.12 °C, November 4.97 °C, October 2.92 °C, April 1.04 °C, September -1.47 °C, July -4.00 °C, August -4.20 °C, May -4.20 °C, June -4.75 °C.
- **Johannesburg relative humidity, highest to lowest:** January 65.13 %, February 64.06 %, December 63.34 %, March 63.04 %, April 62.21 %, November 56.51 %, June 54.65 %, May 54.12 %, July 49.19 %, October 48.19 %, August 43.61 %, September 38.95 %.
- **Johannesburg corrected precipitation, highest to lowest:** December 4.09 mm/day, January 3.95 mm/day, November 2.97 mm/day, February 2.90 mm/day, March 2.36 mm/day, October 1.83 mm/day, April 1.44 mm/day, September 0.53 mm/day, May 0.51 mm/day, August 0.23 mm/day, June 0.23 mm/day, July 0.09 mm/day.
- **Johannesburg 10 m wind speed, highest to lowest:** September 4.26 m/s, October 4.16 m/s, August 4.11 m/s, November 3.88 m/s, July 3.53 m/s, June 3.50 m/s, December 3.36 m/s, May 3.14 m/s, January 3.04 m/s, April 2.97 m/s, February 2.89 m/s, March 2.87 m/s.

## Johannesburg month-to-month screening ledger

- **Johannesburg January:** mean 21.64 °C, change from December +0.19 °C; max–min span 31.79 °C; humidity 65.13%, change +1.79 points; precipitation 3.95 mm/day; wind 3.04 m/s.
- **Johannesburg February:** mean 21.38 °C, change from January -0.26 °C; max–min span 26.34 °C; humidity 64.06%, change -1.07 points; precipitation 2.90 mm/day; wind 2.89 m/s.
- **Johannesburg March:** mean 19.86 °C, change from February -1.52 °C; max–min span 27.71 °C; humidity 63.04%, change -1.02 points; precipitation 2.36 mm/day; wind 2.87 m/s.
- **Johannesburg April:** mean 16.67 °C, change from March -3.19 °C; max–min span 30.32 °C; humidity 62.21%, change -0.83 points; precipitation 1.44 mm/day; wind 2.97 m/s.
- **Johannesburg May:** mean 13.32 °C, change from April -3.35 °C; max–min span 33.51 °C; humidity 54.12%, change -8.09 points; precipitation 0.51 mm/day; wind 3.14 m/s.
- **Johannesburg June:** mean 10.03 °C, change from May -3.29 °C; max–min span 30.16 °C; humidity 54.65%, change +0.53 points; precipitation 0.23 mm/day; wind 3.50 m/s.
- **Johannesburg July:** mean 9.89 °C, change from June -0.14 °C; max–min span 29.81 °C; humidity 49.19%, change -5.46 points; precipitation 0.09 mm/day; wind 3.53 m/s.
- **Johannesburg August:** mean 13.08 °C, change from July +3.19 °C; max–min span 33.99 °C; humidity 43.61%, change -5.58 points; precipitation 0.23 mm/day; wind 4.11 m/s.
- **Johannesburg September:** mean 17.34 °C, change from August +4.26 °C; max–min span 34.86 °C; humidity 38.95%, change -4.66 points; precipitation 0.53 mm/day; wind 4.26 m/s.
- **Johannesburg October:** mean 19.91 °C, change from September +2.57 °C; max–min span 33.77 °C; humidity 48.19%, change +9.24 points; precipitation 1.83 mm/day; wind 4.16 m/s.
- **Johannesburg November:** mean 20.72 °C, change from October +0.81 °C; max–min span 31.92 °C; humidity 56.51%, change +8.32 points; precipitation 2.97 mm/day; wind 3.88 m/s.
- **Johannesburg December:** mean 21.45 °C, change from November +0.73 °C; max–min span 30.01 °C; humidity 63.34%, change +6.83 points; precipitation 4.09 mm/day; wind 3.36 m/s.

Harth retrieved this point climatology from NASA POWER API v2.9.7 for location record 993800. The ranked fingerprint and transition ledger preserve Johannesburg's monthly order and successive changes for source comparison. This 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)
- [Climate Design Data: Pretoria, South Africa](https://harth.build/resources/climate-data/climate-design-data-pretoria-za.md)
- [Climate Design Data: Vereeniging, South Africa](https://harth.build/resources/climate-data/climate-design-data-vereeniging-za.md)
- [Climate Design Data: Carletonville, South Africa](https://harth.build/resources/climate-data/climate-design-data-carletonville-za.md)
- [Climate Design Data: Soshanguve, South Africa](https://harth.build/resources/climate-data/climate-design-data-soshanguve-za.md)
- [All climate & energy design data guidance for South Africa](https://harth.build/resources/climate-data/south-africa.md)
- [House Construction Cost Planning: Johannesburg, South Africa](https://harth.build/resources/construction-costs/house-construction-cost-johannesburg-za.md)
- [Office Construction Cost Planning: Johannesburg, South Africa](https://harth.build/resources/construction-costs/office-construction-cost-johannesburg-za.md)
- [Retail Construction Cost Planning: Johannesburg, South Africa](https://harth.build/resources/construction-costs/retail-construction-cost-johannesburg-za.md)
- [School Construction Cost Planning: Johannesburg, South Africa](https://harth.build/resources/construction-costs/school-construction-cost-johannesburg-za.md)

## Sources and method

Location data from the [GeoNames ZA dump](https://download.geonames.org/export/dump/ZA.zip) (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 993800). Regulatory starting point: [South African Bureau of Standards and the local authority](https://www.sabs.co.za/). Figures are illustrative — verify against the current locally adopted edition for the site. 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=28.04363&latitude=-26.20227&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

- [download.geonames.org](https://download.geonames.org/export/dump/ZA.zip)

- [sabs.co.za](https://www.sabs.co.za/)

- [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=28.04363&latitude=-26.20227&format=JSON)

## Frequently asked questions

### What does NASA POWER climatology show for Johannesburg?

For the Johannesburg reference point, the 2001–2020 NASA POWER climatology reports 17.1 °C annual mean temperature, 55.2% relative humidity and 1.76 mm/day corrected precipitation. The monthly maximum peaks at 38.8 °C in January.

### Can the Johannesburg climatology replace project design temperatures or an hourly weather file?

No. The Johannesburg response is gridded monthly climatology; its lowest monthly minimum of -4.8 °C in June 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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