Ash can provide valuable soil protection. However, ash is also very mobile, and soil protection patterns can be quickly changed, favouring the protection of some areas and exposing others with implications for soil erosion. In this research, the effects of a high severity wildfire on ash thickness were studied, 1 and 15 days after the fire. For this evaluation, several interpolation methods were tested to identify the best spatial predictor of ash distribution. The results showed that 1 day after the fire, ash was thinner in high severity areas. Fifteen days after the fire, ash thickness decreased, and the spatial pattern changed. This implies that evaluation of fire severity based on ash thickness must take a place immediately after the fire because it is affected by (re)distribution. There was an increase in the spatial autocorrelation, and ash distribution corresponded to a specific spatial pattern, because of wind (re)distribution. One day after the fire, the most accurate predictor was Inverse to a Weight 3 (IDW3) that detected easily the small-scale variability of ash thickness, and after 15 days, ordinary kriging identified a specific pattern of ash distribution. Copyright © 2013 John Wiley & Sons, Ltd.