Recent dry conditions have kept London’s May rainfall totals well below the long-term average of 50–60 mm, with only around 5 mm recorded through mid-month according to Met Office monitoring. This positions the market toward the 15–20 mm and 25–30 mm bands as traders weigh the remaining forecast window. Springtime Atlantic low-pressure systems and frontal passages are the main drivers that could deliver the heavier showers needed to push totals higher, while persistent high pressure would favor lighter, more scattered precipitation. Model consensus currently shows moderate rain chances through late May without a strong signal for prolonged wet spells, creating tight competition between those two leading outcomes.