Solar & Daylight Data

Updated 2026-08-31

Sun Path: Cape Town, South Africa

How to research sun path for a specific site in Cape Town — the controlling authority, source documents, and checks to run before you rely on a number.

Last updated August 31, 2026 · 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 3369157). 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. Solar-method context: [NOAA Solar Calculation Details](https://gml.noaa.gov/grad/solcalc/calcdetails.html); the Harth monthly table uses a simpler declination and geometric-daylight approximation whose stated limitations must be retained.

Direct answer

For Cape Town at -33.9258, 18.4232, the declination-only solar-noon altitude is approximately 32.6° at the June solstice, 56.1° at an equinox and 79.5° at the December solstice. Refine these geometry checks with the project date, civil time, facade azimuth, terrain and local horizon. The reproducible location record is GeoNames ID 3369157 in administrative area 11, at -33.9258, 18.4232; replace it with the surveyed parcel point before relying on the result. As a transparent geometry check, declination-only solar-noon altitude is about 32.6° at the June solstice, 56.1° at an equinox and 79.5° at the December solstice. Representative 21st-day geometry ranges from about 9.7 hours in June to 14.3 hours in December; this excludes atmospheric refraction, terrain and obstruction effects. The cited national authority is a discovery starting point; current local documents and a named qualified reviewer control project use of this sun path record.

Prepared by Harth · Prepared from the cited location and country sources; local project inputs remain unreviewed · Published 2026-08-26 · Updated 2026-08-31.

What must be verified for Cape Town?

Cape Town is represented here at approximately -33.9258, 18.4232 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 sun path 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.
InputProject-specific evidenceQA question
Sitesurveyed coordinates, elevation and horizonDoes the point represent the building?
Weather/solar methodnamed dataset, algorithm, period and time basisAre station, time zone and units explicit?
Design scenariocurrent and future scenario agreed by the teamIs an average being mistaken for an extreme?
Complianceadopted local document and editionWas applicability confirmed with the authority?

What are the limits of this worksheet?

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

This primary route consolidates the location evidence needed for Sun Path, Solar Altitude & Azimuth, Solar Shading Design, Daylight & Orientation. A narrower route should be released only when it adds a materially different official source, calculation, process, threshold or worked example.

Cape Town monthly solar geometry check for sun path

Representative dateDeclinationSolar-noon altitudeGeometric daylightNoon shadow / height
21 January-20.14°76.21°13.904 h0.245
21 February-11.23°67.30°13.023 h0.418
21 March-0.40°56.48°12.036 h0.662
21 April+11.58°44.50°10.944 h1.018
21 May+20.14°35.94°10.096 h1.380
21 June+23.45°32.62°9.738 h1.562
21 July+20.44°35.63°10.064 h1.395
21 August+11.75°44.32°10.927 h1.024
21 September-0.20°56.28°12.018 h0.668
21 October-11.75°67.83°13.073 h0.408
21 November-20.44°76.52°13.936 h0.240
21 December-23.45°79.52°14.262 h0.185

Cape Town solar-geometry fingerprint at -33.9258, 18.4232

  • Cape Town, 21 January: declination -20.14°, noon altitude 76.21°, zenith 13.79°, geometric daylight 13.904 hours, and vertical-object noon shadow ratio 0.245.
  • Cape Town, 21 February: declination -11.23°, noon altitude 67.30°, zenith 22.70°, geometric daylight 13.023 hours, and vertical-object noon shadow ratio 0.418.
  • Cape Town, 21 March: declination -0.40°, noon altitude 56.48°, zenith 33.52°, geometric daylight 12.036 hours, and vertical-object noon shadow ratio 0.662.
  • Cape Town, 21 April: declination +11.58°, noon altitude 44.50°, zenith 45.50°, geometric daylight 10.944 hours, and vertical-object noon shadow ratio 1.018.
  • Cape Town, 21 May: declination +20.14°, noon altitude 35.94°, zenith 54.06°, geometric daylight 10.096 hours, and vertical-object noon shadow ratio 1.380.
  • Cape Town, 21 June: declination +23.45°, noon altitude 32.62°, zenith 57.38°, geometric daylight 9.738 hours, and vertical-object noon shadow ratio 1.562.
  • Cape Town, 21 July: declination +20.44°, noon altitude 35.63°, zenith 54.37°, geometric daylight 10.064 hours, and vertical-object noon shadow ratio 1.395.
  • Cape Town, 21 August: declination +11.75°, noon altitude 44.32°, zenith 45.68°, geometric daylight 10.927 hours, and vertical-object noon shadow ratio 1.024.
  • Cape Town, 21 September: declination -0.20°, noon altitude 56.28°, zenith 33.72°, geometric daylight 12.018 hours, and vertical-object noon shadow ratio 0.668.
  • Cape Town, 21 October: declination -11.75°, noon altitude 67.83°, zenith 22.17°, geometric daylight 13.073 hours, and vertical-object noon shadow ratio 0.408.
  • Cape Town, 21 November: declination -20.44°, noon altitude 76.52°, zenith 13.48°, geometric daylight 13.936 hours, and vertical-object noon shadow ratio 0.240.
  • Cape Town, 21 December: declination -23.45°, noon altitude 79.52°, zenith 10.48°, geometric daylight 14.262 hours, and vertical-object noon shadow ratio 0.185.

Harth computed the Cape Town fingerprint for latitude -33.9258° with the Cooper declination approximation, 90° - |latitude - declination| at solar noon, centre-to-centre sunrise hour angle and 1 / tan(altitude) shadow ratio. Longitude 18.4232° is retained for a later civil-time conversion; this screen does not perform that conversion. See NOAA's solar calculation details. Atmospheric refraction, terrain, facade azimuth and obstructions remain outside this first-pass comparison.

Sources and method

Location data from the GeoNames ZA dump (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 3369157). Regulatory starting point: South African Bureau of Standards and the local authority. Figures are illustrative — verify against the current locally adopted edition for the site. Solar-method context: NOAA Solar Calculation Details; the Harth monthly table uses a simpler declination and geometric-daylight approximation whose stated limitations must be retained.

Frequently asked questions

What does the sun path record for Cape Town establish?

The sun path record for Cape Town establishes a reproducible discovery point at -33.9258, 18.4232 (GeoNames ID 3369157, administrative area 11) and a South Africa source path. It does not establish a final project value, approval or parcel decision.

What must be replaced before using this sun path workflow for a project in Cape Town?

For the sun path record in Cape Town, replace the -33.9258, 18.4232 city reference with the surveyed site or parcel, identify the competent local authority, and verify the current documents under National Building Regulations and SANS 10400, as applied by the local authority. Record the edition, retrieval date, units, assumptions and named checker before relying on the result.

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