The first satellite active-fire detection represents an observation event rather than the timing of ignition. We quantified short-term hydroclimatic conditions preceding the first satellite detection of reconstructed tropical peat-fire events and assessed whether Sentinel-1 C-band backscatter provided information beyond hydroclimatic indicators. We analyzed 79 reconstructed non-singleton MODIS/VIIRS fire events in South Sumatra using a time-stratified case-crossover design comprising 79 case dates and 234 same-weekday referents. CHIRPS rainfall, ERA5-Land vapor pressure deficit (VPD) and soil-water indicators, and Sentinel-1 ΔVV were summarized over prespecified windows spanning 60–1 d before the first retained detection (t0). Conditional logistic regression accounted for satellite observation opportunity on the index date, with uncertainty estimated using 2,000 stratum-level bootstrap replicates. The clearest short-term hydroclimatic pattern occurred 1–3 d before t0. An interquartile-range (IQR) increase in VPD was associated with higher case-period odds (odds ratio [OR] 4.07; 95% confidence interval [CI] 1.43–13.54), whereas a wetter rainfall anomaly was associated with lower odds (OR 0.66; 95% CI 0.45–0.86). Lower absolute rainfall and a greater frequency of dry days supported the same drying pattern. Although lag-specific p values did not remain below 0.05 after multiplicity adjustment, shared-bootstrap contrasts indicated stronger standardized associations at 1–3 d than, on average, across longer antecedent windows. Sentinel-1 ΔVV did not materially improve model fit after hydroclimatic adjustment, although earlier-window backscatter changes showed concordance with gridded soil-water conditions. Overall, the findings support a temporally concentrated hydroclimatic drying signal before first satellite detection, without resolving ignition timing. Hydroclimatic indicators provided the clearest near-term information, while Sentinel-1 contributed complementary moisture-sensitive evidence.