Prolonged drought and repeated heatwaves across the Rhine basin have driven water levels at key gauges like Kaub to record lows near 15-40 cm in early-to-mid August 2026, far below the roughly 1.5-2 m thresholds needed for normal commercial navigation and well under the 77 cm economic viability line. Low Alpine snowpack from the prior winter, combined with minimal summer rainfall, has left the river reliant on future precipitation for recovery, with short-term forecasts showing only brief, limited rebounds rather than sustained rises. Traders price the October window highest because historical patterns and current hydrology models point to gradual autumn rains as the most probable trigger for normalization, while the sizable share on “not by November 1” reflects uncertainty over whether seasonal deficits will persist into late fall or require winter snowmelt. Tight spreads among September and October buckets underscore the narrow window for any meaningful turnaround before colder weather sets in.