Every day across the western US and Canada, over 900 SNOTEL stations quietly record how much new snow fell overnight. Taken individually, each reading is a single data point. Taken together across a full winter season, they tell the story of every storm that moved through the mountains — where it hit, how hard, and how it spread.
The animation below maps that story. Each frame is one day of the 2025–26 winter season, with each dot representing a SNOTEL station sized and colored by how much new snow fell that day. Hit play and watch the storms roll through.
Daily new snow (inches) at SNOTEL stations across the western US · Winter 2025–26 · Data: USDA NRCS via OutsideDB · Use the play button or drag the date slider to scrub through the season
How It Was Built
The animation pulls directly from the OutsideDB PostgreSQL database, which stores daily readings from all 911 SNOTEL stations in the NRCS network. New snow for each day is calculated as the positive difference in snow depth between consecutive readings — effectively isolating fresh accumulation while ignoring settlement and melt.
A short Python script queries the database, calculates daily new snow per station, then passes the result to Plotly — an open-source graphing library that handles the animated scatter map in a single call. Plotly's animation_frame parameter steps through each date automatically, generating the play button and date slider with no additional code. The output is a self-contained HTML file with all the data and interactivity built in.
The dark map background is Carto's Dark Matter tile layer, which makes the blue snow accumulation dots stand out clearly against the terrain. Dot size and color both scale with accumulation, so larger storms are immediately visible. Readings are capped at 40 inches to prevent sensor outliers from dominating the scale.
The whole pipeline — database query to animated HTML — runs in under a minute. We plan to update this periodically through the season and explore expanding it to include BC Ministry of Environment snow stations as well.