The position of the sun is expressed in altitude (or elevation) and azimuth, both of which will vary by location, time of day, and time of year. Altitude refers to the height of the sun over the horizon (higher in the summer, lower in the winter) and is expressed in degrees. Azimuth refers to the direction of the sun. In the northern hemisphere, the azimuth of the sun changes over the course of a day from east in the morning (azimuth ~ 90 deg.), to south at noon (~ 180 deg.) to west in the evening (~270 deg.).
There are several websites that are useful in determining the position of the sun at a given location. One of the easiest to use is the Sun or Moon Altitude/Azimuth Table from the U.S. Naval Observatory. A helpful feature of this sun position calculator is that users can enter a city for their location, rather than latitude and longitude, which many other calculators require. To determine the highest altitude of the sun in the northern hemisphere for summer, enter noon on June 20 as the date/time; for the lowest position in winter, enter noon on December 21.