The answer to whether it snows in summer is unequivocally yes, but the occurrence depends entirely on geographical and atmospheric conditions. For the Northern Hemisphere, summer is generally defined as the period between June and August, yet snowfall remains a regular phenomenon in many regions. The presence of snow is governed by a specific set of meteorological factors, including temperature, altitude, and moisture, rather than the calendar alone.
The Physics Behind Off-Season Snowfall
Snow formation in any season requires the atmospheric temperature to be at or below the freezing point of 0 degrees Celsius. The most important factor is the altitude of the 0°C isotherm, which is the line in the atmosphere where temperatures drop to freezing. Snowflakes form well above the ground in colder air layers and fall through the atmosphere. They will only survive the descent if the air column below the cloud base is cold enough to prevent them from melting completely into rain.
Temperature naturally decreases with increasing altitude, a principle quantified by the environmental lapse rate. This rate averages approximately 6.5°C of cooling for every one kilometer of elevation gain in the lower atmosphere. Consequently, even on a warm day at sea level, the air just a few kilometers higher is cold enough for precipitation to freeze.
The survival of the snowflake also depends on the depth of the melting layer, the zone between the 0°C isotherm and the ground. If the air near the surface is only slightly above freezing, the falling snow may cool the air around it through evaporative cooling. This cooling effect slows the melting process, allowing the frozen precipitation to reach the ground before fully turning into liquid water.
High Altitude and Polar Zones
In many parts of the world, summer snow is a predictable feature of the local climate. High-altitude mountain ranges maintain cold temperatures year-round, keeping the 0°C isotherm close to the ground, even in July. The Andes Mountains, the Rocky Mountains, and the Alps all have peaks and passes where snow is common during the summer months.
These regions possess perennial snowpacks because the high elevation permanently shortens the distance snowflakes must fall through warm air. For instance, in the Rockies, snow flurries can occur at elevations above 3,000 meters throughout the summer. Many glaciers and high-altitude ski resorts in the European Alps, such as those in Austria and Switzerland, offer summer skiing because the permanent ice field is constantly replenished by snowfall.
The polar zones also experience summer snowfall. In the Arctic and Antarctic, summer daylight is nearly continuous, but air temperatures remain near or below freezing. The proximity to the poles means that the atmospheric conditions necessary for snow are always present, regardless of the solar angle. Additionally, regions in the Southern Hemisphere, such as the mountainous areas of Chile, Argentina, and New Zealand, experience their winter during the Northern Hemisphere’s summer.
Rare Instances in Temperate Regions
Summer snowfall in low-lying, temperate zones is a highly unusual occurrence, often resulting from anomalous meteorological patterns. These events require an extreme influx of cold air, typically driven by a deep trough in the jet stream. Such a pattern allows frigid Arctic air to plunge much farther south than its normal summer boundary.
These cold air outbreaks must combine with a source of moisture to produce snow. When this happens, the 0°C isotherm is temporarily forced down to a much lower elevation than is typical for the season. For example, parts of the United States Midwest and intermountain West have seen June or July snowfall when severe cold fronts push through the region.
The “Year Without a Summer” in 1816 is a historic example, where summer snow and frost were reported across New England and Europe. This exceptional cold was caused by the massive 1815 eruption of Mount Tambora, which injected ash and sulfur dioxide into the stratosphere, blocking solar radiation globally. These events are extreme, low-probability deviations from the seasonal norm, not typical weather.