Lake-Effect Season Is Beginning And We're Not Talking About Snow

Did You Know Lake-Effect Isn’t Just Snow?

As the seasons begin to change, so do the weather patterns across the country. That autumn temperature change prompts the start of the lake-effect season in the Great Lakes region, and we're not talking about lake-effect snow.

Yes, we will see lake-effect snow soon enough, but first, we begin with lake-effect rain.

What Is Lake-Effect Precipitation?

For lake-effect precipitation to occur, there has to be cold air in place. During the fall months, cold fronts begin to infiltrate southward over the Great Lakes. This brings in the cold air needed for lake-effect precipitation. As this happens, the lake water temperatures remain relatively warm compared to the air above.

The lake water adds moisture and warmth to the cold, dry air, which results in instability and rising air, causing clouds and precipitation to develop.

In addition, winds also need to be blowing in nearly the same direction throughout the lower atmosphere, and strong wind speeds are not ideal.

Early in the season, until temperatures drop below freezing and are cold enough to produce snow, the Great Lakes region will receive lake-effect rain. Just as lake-effect snow, this can result in a wet pattern for several days at a time.

Given the right conditions, thunder, heavy rainfall and even waterspouts can also occur, particularly in early fall.

Waterspouts, which are a type of tornado, are fairly common in the Great Lakes during the fall, which locals refer to as "waterspout season."

(MORE: What Is Waterspout Season?)

Waterspout season runs from late July through the middle of October, and the number of waterspouts can be quite impressive. On Oct. 20, 2013, there were 67 individual waterspout sightings on the Great Lakes!

When Lake-Effect Rain Turns To Snow

These conditions are more likely to be in place later in the season, after a strong cold front pushes through the Great Lakes region, dropping temperatures cold enough to produce snow.

(MORE: What Is Lake-Effect Snow?)

Sleet and graupel can also form depending on the temperatures the precipitation encounters as it falls to the ground.

The direction of the wind plays an important role in how much and where precipitation occurs. When the trajectory of the cold air takes it along a longer path over the lake, thicker clouds can grow.

Bands of rain and snow will set up in relation to the wind direction and can result in big differences in precipitation amounts over a small distance.

One particularly noteworthy example of this took place Nov. 17-21, 2024. This lake-effect snow event buried parts of the Buffalo, New York, metro area in snow as the region was slammed by back-to-back lake-effect snowstorms which combined to dump up to 88 inches of snow.

At times, 6 inches of snow fell per hour. Hundreds of major roof collapses and structural failures occurred due to the weight of the snowpack, according to the National Weather Service. Numerous trees also were damaged, leading to isolated power outages. It's referred to by many as "Snowvember."

Even when precipitation doesn't form, the increase in cloud cover can result in gloomy conditions, especially heading into November. This is the case during the fall due to the higher relative humidity values at this time of year, as temperatures cool down over lakes that are still unfrozen.

Once the lakes freeze over, the lake-effect snow machine turns off for the season. This typically occurs around February, but can vary from season to season.