Trader consensus on May precipitation totals for London remains tightly balanced between the 15-20 mm and 25-30 mm brackets because early-month rainfall has run below the 50 mm climatological average under a blocking high-pressure regime, yet medium-range models show increasing potential for Atlantic fronts to deliver additional accumulation after mid-month. Ensemble guidance highlights uncertainty in jet-stream positioning and North Atlantic Oscillation phase, which historically produces wide variability in May rainfall amounts. Official Met Office forecasts emphasize that any shift in storm-track timing or intensity over the next week could alter final totals, keeping the two leading outcomes nearly even while lower and higher brackets trail on current data.