Flood risk communication has increasingly emphasized technical precision and hazard forecasting. However, a crucial dimension—how individuals perceive and respond to uncertainty—remains underexplored. In this study we introduce the Uncertainty Lens Framework (ULF) to systematically explore how uncertainty perception shapes threat, ownership, and coping appraisals in flood risk contexts. Drawing on concepts from Protection Motivation Theory (PMT), decision heuristics, and the Safe Development Paradox (SDP), we demonstrate that perceived uncertainties rather than the objective ones alone critically influence decision-making and action. Using the 2021 flood event in Germany as an empirical case, we analyse statements from affected individuals to reveal how uncertainty perception can reinforce mal-adaptive responses. Our findings highlight three core illusions of safety: past flood and warning experience, delegated responsibility, and institutional preparedness that are driven by heuristics and amplified by gaps in uncertainty acknowledgement and communication. We argue for proactive uncertainty management that does not seek to eliminate uncertainty, but rather to integrate it meaningfully into risk communication and policy design to support adaptive and anticipatory responses. For this we highlight the need to purposefully set anchors and availabilities supporting in contextualising uncertainty stemming from immediate and future possible threat.