a few more words on how a custom effect can be added

usermods/usermod_v2_weather/readme.md

@@ -2,6 +2,29 @@
 
 In this usermod file you can find the documentation on how to take advantage of the new version 2 usermods!
 
+### adding usermod specific effects
+
+This usermod also provides an example on how to add your own effects in a usermod.
+* the new effect code is in this function, similar to other effects fx.cpp:
+```c++
+//effect function
+uint16_t mode_2DWeather(void) { 
+
+....
+
+  return FRAMETIME;
+}
+static const char _data_FX_MODE_2DWEATHER[] PROGMEM = "Weather@;!;!;pal=54,2d"; //temperature palette
+```
+* then activated in the usermod setup function 
+```c++
+class WeatherUsermod : public Usermod {
+  public:
+    void setup() {
+      strip.addEffect(255, &mode_2DWeather, _data_FX_MODE_2DWEATHER);
+    }
+```
+
 ## Installation 
 
 Copy `usermod_v2_example.h` to the wled00 directory.