Since 2000, wildfires in the western United States have increased in both frequency and intensity due to hydro-meteorological shifts, prolonged drought, and expanded human activity. Although geostationary systems enable rapid detection and moderate-resolution sensors offer broad coverage, a gap persists for high-spatial-resolution thermal observations that can assess fine-scale fire behavior. The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) provides 70-meter land surface temperature (LST) observations with 1–5 days average revisit intervals, providing enhanced spatial detail for active-fire analysis. In this study, we evaluate the capability of ECOSTRESS Level 2 LST data, which uses 5 thermal bands, to characterize wildfire behavior across four California fires: Carr (2018), Kincade (2019), August Complex (2020), and Dixie (2021). We developed a consistent framework to identify hotspots (LST ≥ 60 ° C ), estimate a satellite-derived rate-of-spread (ROS) proxy using the 95th percentile radial expansion from ignition, and assess relationships between mean active-fire temperature and mean post-fire burn severity (dNBR). Across all fires, median hotspot temperatures ranged from 62 to 77 °C, while 95th percentile values ranged from 117 to 179 °C, indicating right-skewed radiometric distributions. The ROS proxy showed directional variability, with median values typically between 0.05 to 3 km day−1 and substantial heterogeneity among quadrants. Regression indicates consistent positive relationships between mean active-fire temperature and mean burn severity, with R 2 values from 0.51 to 0.88. These relationships were stronger in smaller, short-duration fires. Additionally, the ECOSTRESS derived hotspots were validated against Fire Radiative Power (FRP) data derived from VIIRS, and it was demonstrated that ECOSTRESS-derived thermal anomalies are spatially coherent with independently derived FRP intensity patterns. Our findings indicate that ECOSTRESS provides valuable high-spatial-resolution thermal observations that can resolve fire growth patterns and link active-fire thermal dynamics to subsequent burn severity.