The Tempest device uses our patented haptic rain sensor technology that quantifies rainfall by measuring the force of raindrops impacting the top of the device. With no moving parts to clog, break or deteriorate it requires little to no maintenance. Tempest also measures the duration of each rain event, down to the minute, including the relative intensity ranging from very light to extreme rainfall. And the Tempest System can send a rain alert as soon as it starts to rain.
Total daily rain accumulation, starting at midnight local time, is updated every minute. When the daily total is small enough that it would round to zero, the Tempest apps will display “Trace” instead. Rain accumulation is also reported in weekly, monthly, yearly and “all time” time ranges.
Tempest reports the current rain rate as both a qualitative value (none, trace, very light, light, moderate, heavy, very heavy, extreme) and a quantitative value (inches/hour or cm/hour or mm/hour). This current rate is updated every minute.
Unlike other rain sensors that use the tipping bucket or tipping spoon concept, the haptic sensor records the total rain duration down to the minute, broken down by rain intensity. Tempest can tell you how much “heavy” vs “light” rain you receive, for example.
Historical Rain Data
Like all Tempest parameters, data is stored over time and can be viewed in graphs and tables in order to look into totals & extremes over time, or compare one month to another, or one year to another and so on.
Rain Start Alerts
“Rain Start” alerts are enabled by default for each station and can be disabled in the app. A push notification is sent when the Tempest System, using data from your station as well as other sources, determines that it’s raining at your location. A new rain alert will not be sent unless it stops raining for at least 15 minutes. Rain start alert sensitivity is adjustable and set low by default to prevent rain alerts during sporadic or very light rain.
Frozen Precipitation (Snow, Graupel, Sleet & Hail)
The haptic rain sensor does not detect or measure snow because snow is generally too light to produce a signal. The sensor does detect graupel, sleet & hail and while research is underway that may lead to reporting and categorizing frozen precipitation detection, algorithms in the Tempest System currently filter this signal out.
A unique feature of the Tempest System is the reporting of daily rainfall at the neighborhood scale, rather than just the rain that landed exactly on your Tempest device. Because rainfall can vary greatly over small distances, the value reported by an individual Tempest device is not always the best estimate of the rain received at the scale of your property or neighborhood. The NC Rain value is influenced by the measurements from your Tempest device and also considers other measures of precipitation such as radar, professional rain gauges and nearby Tempest devices. See Nearcast Rain for full details.
The Tempest haptic sensor design mitigates issues with small tipping bucket rain gauges, including under-catch in windy conditions, splash and spill-over when tips can’t keep up with very heavy rain. Rain accumulation accuracy will typically agree with a professional-grade, co-located rain gauge, although it can deviate at the extreme ends of intensity (very light rains and torrential downpours).
In areas where it rains regularly, the Tempest rain sensor is effectively self-cleaning. There are no moving parts to bind or break and no funnels to clog. In areas that experience long periods without rain, you may need to periodically remove any dust and grime that might have accumulated on your Tempest.
For troubleshooting & calibration guides for Tempest's haptic rain sensor, see Troubleshooting Measurements & Data.