As the nation basks in some of the warmest February weather it has seen in decades, the U.S. Geological Survey is being quick to point out that the early spring conditions are just another symptom of climate change.

The USGS shared a new analysis just released by the USA-National Phenology Network, which the agency helps to fund, showing that an early spring has already swept through the Southeast and is continuing to work its way across the country. As the agency points out, the analysis reaffirms a fact scientists have known for at least a decade now — that “climate change is variably advancing the onset of spring across the United States.”

The analysis relies on a special “spring index,” which defines the start of spring as the point when temperatures allow for certain early-season events in plants, such as the emergence of leaves and blooms. The index was created using data that’s been collected for a citizen science project over the past few decades, according to Jake Weltzin, executive director of the USA-National Phenology Network and an ecologist with the USGS, which helped fund the project.

Since the 1950s, volunteers have been collecting information about the leafing and blooming of certain plants, such as lilacs and honeysuckle, Weltzin said. More recently, climatologist Mark Schwartz of the University of Wisconsin-Milwaukee used this information to develop an algorithm that can now be used with national temperature data to determine where and when “spring” has arrived across the country.

By comparing this year’s temperatures with data from previous years, the scientists are able to determine which locations are seeing an unusually early spring compared to the average. Washington, D.C., for instance, saw its spring arrive a whopping 22 days early, according to the analysis.

In general, the new season has already made its appearance throughout most of the Southeast and as far north as southern Illinois and Indiana. It’s now starting to show up scattered locations across the Western states, including in parts of Colorado, New Mexico and Arizona, and has even begun to creep into California.

The findings are all just another way of pointing to the progression of climate change, Weltzin noted. He also noted that, while the balmy conditions may seem nice on the surface, an early spring can come with all kinds of downsides. For one thing, the onset of warm weather is also associated with the reemergence of disease-carrying parasites and insects.

There are other indicators of the long-term climatic changes that are happening in the U.S., Weltzin noted. But the onset of spring remains one of the more dramatic red flags.

Chelsea Harvey is a Washington Post writer.