Trader consensus favors 30mm+ total precipitation at 53.5% implied probability for May in London, driven by an exceptionally dry start with just 2-5mm recorded at Heathrow and local stations like NW3 through May 13—far below the climatological ~20mm for the first half—yet offset by Met Office forecasts of persistent heavy showers and thunder persisting through late May under low-pressure dominance. This positions the market above drier bins like 10-15mm (40.9%), reflecting uncertainty in remaining ~17 days where model ensembles indicate above-normal rainfall potential to approach the 46mm monthly norm, amid cooler anomalies (+1.6°C) and Atlantic moisture influx following 2026's wet winter. Key watchpoints include daily Met Office advisories and ensemble shifts for shower coverage.