**Trader sentiment for Singapore’s highest temperature on June 15, 2026, centers on 31°C (46% implied probability) and 30°C (29.5%), reflecting expectations that afternoon thundery showers will cap daytime heating.** The Southwest Monsoon has brought increased convective activity, with official NEA and Meteorological Service Singapore guidance forecasting thundery showers over many areas during late morning and early afternoon on June 15. These showers reduce incoming solar radiation, promote evaporative cooling, and limit the development of extreme surface heating typical of clearer monsoon days. Recent heavy rainfall on June 12, which produced a sharp drop to 20.1°C in parts of the island, has reinforced trader caution about rapid temperature moderation. While background El Niño conditions and a developing positive Indian Ocean Dipole have supported above-average warmth and reduced rainfall earlier in June—pushing some daily maxima to 34°C—local-scale cloud cover and instability introduce meaningful uncertainty that favors outcomes near or slightly below the long-term June average high of approximately 31°C. Official outlooks still allow for 33–34°C on days with limited cloud cover, but the current consensus of shower timing and coverage keeps the market weighted toward 30–31°C. New model runs and updated 24-hour forecasts from NEA/MSS will provide the next key signals as resolution approaches.