Rain Check is a free and an optional bonus tool in the app. Because rainfall can vary so greatly over small distances, the goal of Rain Check is to provide a representation of daily rainfall at the "neighborhood" scale, rather than just the rain that landed exactly on your Tempest device. The Rain Check accumulation value starts with and depends on raw data from the haptic sensor in your Tempest, but it also considers other measures of precipitation in your area (including other Tempest devices).
Rain Check data is provided in the app each and every day in the AM hours (exact times may vary depending on weather conditions), Rain Check compares the raw accumulation calculations from the haptic rain sensor against a reference data set described below to create an accurate representation of the average rainfall for your location.
It does not erase the saved raw data derived from the haptic rain sensor but it does replace the accumulation value shown in the app. You’ll know if you're seeing Rain Check data if the logo appears next to the rain accumulation value in the app.
The Rain Check system currently only applies to stations located in the continental United States and some parts of Canada. WeatherFlow will continue efforts to make Rain Check or similar data available in other areas of the globe.
Rain Check accuracy has a lower confidence score in areas where brief showers/thunderstorms are frequent and large terrain influence is present.
Rain Check can be enabled or disabled in the app under the advanced device settings: go to settings > stations > choose your station > manage devices > choose your Tempest or SKY device > advanced > toggle Rain Check feature on/off.
A well-calibrated haptic sensor, in SKY or Tempest, installed on a stable mounting position, free of vibration, will produce rain accumulation values that are remarkably good. Rain Check will improve the accumulation values in cases where a particular device is not ideally mounted, which is difficult to do in most home locations (see these siting & installation tips for more details). If you believe your haptic sensor is experiencing significant accuracy issues over multiple rain events, please contact customer service.
Rain Check is a proprietary system that combines WeatherFlow device data with sophisticated 3rd party precipitation models that integrate up to seven (7) key precipitation data inputs to produce the most accurate rain accumulation estimate for a particular location. Precipitation inputs include: a reference network of over 25,000 quality-controlled precipitation gauges, climatological basemaps to account for complex terrain influences, a mosaic of state-of-the-science dual-pol estimated precipitation derived from NEXRAD radar sites, level-II radar reflectivity translated into a rainfall rate using standard Z-R algorithms, isopercental interpolation estimates in areas of complex terrain without adequate radar coverage, low altitude radar beam confidence rating to determine spatial suitability, and satellite rainfall estimates from NOAA’s Center for Satellite Applications and Research (STAR) known as “Hydro-Estimator”.