The temperature difference between Chicago and San Salvador, El Salvador, is significant. Chicago experiences a vast range of temperatures, from severe winter cold to warm, humid summers, while San Salvador maintains a stable, year-round tropical climate with minimal seasonal variation. This contrast results from three interconnected geographical and atmospheric elements: Chicago’s position far from the equator, its location deep within a large continental landmass, and its exposure to the dynamic movement of global air masses.
Latitude and Solar Energy Input
The fundamental reason for the temperature disparity is the distance of each city from the equator. San Salvador sits at a low latitude of approximately 13.7 degrees North, placing it within the tropics. Chicago is located much farther north at about 41.8 degrees North. This difference dictates the amount of solar energy each location receives throughout the year.
The sun’s rays strike San Salvador at a high angle of incidence, concentrating the incoming solar radiation (insolation) over a small surface area. This high concentration ensures consistent, warm temperatures year-round. In contrast, Chicago receives sunlight at a much lower angle, especially during winter. This lower angle causes the solar energy to be spread out, or diffused, over a far greater surface area of the Earth.
This less concentrated solar energy input results in lower overall temperatures and a dramatic seasonal swing in Chicago’s weather. San Salvador’s tropical location means the length of the day and the angle of the sun do not change substantially, preventing the significant temperature drops that define Chicago’s winters.
Continental Climate Extremes
Chicago’s position deep within the North American continent results in a continental climate, characterized by greater temperature extremes. Land heats and cools much more rapidly than water, meaning Chicago’s winter temperatures plummet without the moderating effect of a large body of water. The city’s distance from the Atlantic and Pacific Oceans allows the land to become extremely cold during the long winter months, leading to a large annual temperature range.
Although Chicago is on the shores of Lake Michigan, this body of water is not large enough to prevent severe continental temperature swings. While the Great Lakes can slightly delay the onset of seasonal extremes and are a source of lake-effect snow, they cannot store the massive amount of heat necessary to buffer against deep continental cold. San Salvador is close to the Pacific Ocean and the Caribbean Sea. The high heat capacity of these large tropical oceans constantly warms the surrounding air masses, contributing to the city’s stable, narrow temperature range.
The Role of Global Air Masses
The circulation of global air masses directly influences the weather dynamic in both cities. San Salvador is situated within the influence of the Hadley Cell, a large-scale atmospheric circulation pattern in the tropics. This cell involves warm, moist air rising near the equator and then descending as warmer, drier air around 30 degrees latitude, keeping San Salvador consistently bathed in warm, tropical air masses.
Chicago is located in the middle latitudes, acting as a transition zone where different air masses frequently collide. The city sits on the path of cold, dry continental polar (cP) and continental Arctic (cA) air masses that originate over northern Canada and the Arctic. These masses move south unimpeded across the flat interior of the continent, bringing dramatic and sudden temperature drops, often intensified by polar vortices.
The severe cold in Chicago results from the frequent invasion of these cold fronts, which rapidly displace warmer air. San Salvador’s location south of the subtropical high-pressure belt shields it from these polar intrusions, maintaining its stable climate. The resulting collision of Arctic air with warmer, tropical air from the Gulf of Mexico creates the extreme, unpredictable temperature variability characteristic of Chicago’s weather.