How to get a custom alert to trigger when a temperature exceeds or decreases below a particular threshold
WeatherCat custom alerts provide what appears to be an easy way to determine when a temperature exceeds or falls below a certain threshold. However, if you need to restart WeatherCat periodically (for example for system maintenance,) you will discover that WeatherCat will give "false triggers" if WeatherCat is restarted and there is an alert with a temperature rule that is "nearby." To avoid alerts unless the temperature has precisely exceeded or fallen below a particular criteria, you can use a 3-rule alert like this:
This set of alert triggers works by first bounding the temperature range where the alert can trigger to a narrow range (in this case between 30 and 30.2 degrees Fahrenheit.) It then uses the Rising Faster Than test to see if indeed the temperature was increasing when it entered this interval. These three rules will provide a more precise alert trigger. The equivalent set of 3 triggers for a temperature falling event is shown below:
This combination of 3 rules will trigger custom alerts with very high reliability.