I'm the Lead of Developer Support at PowerVR.
We noticed an issue on our devices. When using WebGL in Windy particles don't appear on our devices.
Windy uses mediump in the WebGL shaders to calculate particle positions in the vertex shaders.
Medium (16bit float) precision is usually insufficient for usage in vertex shaders and for texture coordinate calculation.
For more information see section 4.5 in our PowerVR Performance Recommendations: http://cdn.imgtec.com/sdk-documentation/PowerVR.Performance Recommendations.pdf
Can you please change your shaders to highp?