| Summary: | The remote sensing of fire severity and burned area is fundamental in the evaluation of fire impacts. The current study aimed to: (i) compare Sentinel-2 (<i>S2</i>) spectral indices to predict field-observed fire severity in Durango, Mexico; (ii) evaluate the effect of the compositing period (1 or 3 months), techniques (average or minimum), and phenological correction (constant offset, <i>c</i>, against a novel relative phenological correction, <i>rc</i>) on fire severity mapping, and (iii) determine fire perimeter accuracy. The Relative Burn Ratio (<i>RBR</i>), using <i>S2</i> bands 8a and 12, provided the best correspondence with field-based fire severity (<i>FBS</i>). One-month <i>rc</i> minimum composites showed the highest correspondence with <i>FBS</i> (R<sup>2</sup> = 0.83). The decrease in R<sup>2</sup> using 3 months rather than 1 month was ≥0.05 (0.05–0.15) for <i>c</i> composites and <0.05 (0.02–0.03) for <i>rc</i> composites. Furthermore, using <i>rc</i> increased the R<sup>2</sup> by 0.05–0.09 and 0.10–0.15 for the 3-month <i>RBR</i> and <i>dNBR</i> compared to the corresponding <i>c</i> composites. <i>Rc</i> composites also showed increases of up to 0.16–0.22 and 0.08–0.11 in kappa values and overall accuracy, respectively, in mapping fire perimeters against <i>c</i> composites. These results suggest a promising potential of the novel relative phenological correction to be systematically applied with automated algorithms to improve the accuracy and robustness of fire severity and perimeter evaluations.
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