Solar Altitude and Azimuth Explained

Solar Altitude and Azimuth Explained

Direct answer

Definitions of solar altitude, azimuth, and solar noon, and how they change with season and latitude — with computed noon-altitude values for the solstices and equinox.

Key facts

Two angles that locate the sun

Every sun position is defined by two angles measured from where you stand:

• Solar altitude is the angle of the sun above the horizon. It is 0 degrees at sunrise and sunset and reaches its daily maximum at solar noon.
• Solar azimuth is the sun's horizontal bearing, measured as a compass direction. It tells you which facade the sun is facing at any moment.

Solar noon

Solar noon is when the sun crosses the meridian and hits its highest point of the day — due south in the northern hemisphere. Because it is the daily peak, the noon altitude is the single most useful number for shading design. At solar noon the altitude is:

$$ \text{noon altitude} = 90 - |,\text{latitude} - \text{declination},| $$

where solar declination is about +23.44 degrees at the summer solstice, 0 degrees at the equinoxes, and -23.44 degrees at the winter solstice.

Solar-noon altitude by latitude (computed)

The table below applies the formula above. Values are approximate — they use mean declination and ignore atmospheric refraction.

Reading down a column shows how the sun sinks lower as you move toward the poles. Reading across a row shows the seasonal swing — always about 46.9 degrees between the two solstices, twice the axial tilt.

Why this matters in design

• A high summer noon altitude means a modest horizontal overhang can shade south glazing at the hottest time of year.
• A low winter noon altitude means that same overhang still admits low-angle winter sun for passive heating and daylight.
• Low-latitude sites face near-overhead summer sun (little help from vertical shading) but strong east/west low-angle exposure; high-latitude sites deal with low sun year-round and long shadows.

For a full worked example, see sun path and solar angles for Phoenix, AZ, and read understanding sun-path diagrams for how these angles are plotted.

Frequently asked questions

What is solar noon, and is it the same as clock noon?

Solar noon is the instant the sun crosses the local meridian and reaches its highest altitude of the day — due south in the northern hemisphere, due north in the southern. It is almost never exactly 12:00 on the clock: it shifts with your longitude within a time zone, with daylight saving time, and by up to about 16 minutes over the year due to the equation of time. For design geometry, solar noon is the moment that matters because it fixes the day's peak sun altitude.

How do altitude and azimuth change with season and latitude?

Altitude rises in summer and falls in winter because the sun's declination swings between +23.44 and -23.44 degrees. Moving toward the poles lowers the whole envelope: at higher latitudes the noon sun is lower year-round and the azimuth sweeps through a wider arc in summer, with the sun rising well north of east and setting well north of west. Near the equator the noon sun passes close to overhead and the seasonal swing is small.

Why is the winter noon sun so much lower than the summer sun?

The difference is twice the axial tilt — about 46.9 degrees — between summer and winter solstice noon altitude at any latitude. That large swing is exactly why fixed horizontal overhangs work: a device sized to block the high summer sun will still let the much lower winter sun reach the glass and warm the space.

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Source & method: NOAA Solar Calculator / standard solar geometry equations. Noon altitude computed as 90 - |latitude - declination|, with declination taken as +23.44 (summer solstice), 0 (equinox), and -23.44 (winter solstice). Values are approximate and ignore atmospheric refraction and the equation of time.