Understanding Accumulation Weather Parameters: Rain, Snow, Sleet

Tomorrow.io Team
Tomorrow.io Team
  • Updated

Welcome to our guide on weather parameter accumulation. Here, we break down the specifics of snow and ice accumulation, helping you accurately interpret and use this data in your applications.

Precipitation Accumulation

  • Overview: We categorize precipitation into four types: rain, freezing rain, ice pellets, and snow. Accumulation data is updated frequently and is calculated differently for past, present, and future time frames to provide the most accurate forecasts.
  • Calculation: Accumulation is measured hourly, with past data derived from observations and future forecasts from predictive models. Each precipitation type is accumulated separately to ensure clarity and accuracy in forecasts.

Snow Accumulation

  • Definition: Snow Accumulation refers exclusively to the amount of solid snow falling within a specific time frame. It does not include sleet, freezing rain, or ice pellets. Our approach is to ensure that users receive precise information, as different precipitation types have distinct safety implications and physical properties.
  • Best Practice: Use the Snow Accumulation field to display predicted snowfall amounts. This ensures users are informed about snow-specific forecasts without the confusion of including other precipitation types.

Snow Depth

  • Definition: Snow Depth measures the current depth of snow on the ground, considering various factors like compaction, temperature changes, and new snowfall. This dynamically calculated variable provides insight into the existing snowpack's state rather than the amount of falling snow.
  • Usage: Relevant for both current conditions and forecasts, the Snow Depth field helps predict how accumulated snow will impact ground conditions over time. For daily forecasts, it indicates the maximum expected snow depth within a 24-hour period.

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Displaying Snowfall in the Platform

  • Hourly and Daily Snowfall: For applications aiming to show comprehensive snowfall predictions (including all solid precipitation types), focus on using the Snow Accumulation field. Remember, incorporating ice pellets or freezing rain with snow accumulation might not always provide a clear picture due to their distinct impacts.
  • Daily Snowfall Accumulation: To display daily snowfall totals, use the Snow Accumulation parameter. This reflects the sum of snowfall over the day and is distinct from the Snow Depth measurement, which indicates how much snow is present on the ground. Read more about the benefits of displaying accumulation map tiles here.

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Handling Multiple Precipitation Types

While it's rare, there can be instances where more than one precipitation type is recorded in the same hour. However, for clarity and user safety, it's recommended to treat each type separately rather than combining them into a single forecast. Check out our API documentations for more information.



For the most accurate and user-friendly display of weather information, it's advisable to:

  • Use Snow Accumulation for forecasts specific to snow.
  • Keep Ice Accumulation and Snow Accumulation separate to accurately represent their differing effects.
  • Employ Snow Depth data to convey how long snow might remain on the ground.

Need more info or assistance with weather data integration? Contact support@tomorrow.io or your account manager.

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