Touch input processing for touch-sensitive devices can be improved by filtering unintended contact detected on a touch-sensitive surface. In wet environments in particular, water on the touch-sensitive surface can be erroneously detected as touch input and degrade touch performance. In some examples, input patches can be classified as touch patches or non-touch patches prior to computationally-intensive touch processing. Filtering out unintended touches classified as non-touch patches can reduce processing requirements and save power. Additionally, classifying input patches can improve touch performance in wet environments. In some examples, input patches can be classified as touch patches or non-touch patches based on characteristics of edge touch nodes. In some examples, input patches can be classified as touch patches or non-touch patches based on a state-based signal threshold.