Persistent high-pressure dominance has produced an exceptionally dry start to May 2026 in London, with official totals through mid-month at only 1–3 mm against the 46 mm long-term average. This early deficit underpins the tight clustering of market-implied probabilities around the 15–20 mm and 25–30 mm brackets. Ensemble forecasts from the Met Office and ECMWF indicate a modest uptick in Atlantic-driven showers for the final two weeks, yet overall model consensus still points to below-average accumulation for the month. Minor shifts in jet-stream position or the arrival of a slower-moving front could add several millimeters, preserving the current balance between the two leading outcomes.