Pakistan Meteorological Department forecasts an ongoing heatwave persisting through May 19, driven by continental air advection and upper-level subsidence that promote strong solar heating and minimal cloud cover across Karachi. This setup supports peak temperatures in the 35–37°C range on May 17, positioning 37°C or higher as the leading outcome amid 37–40% market-implied odds. Ensemble model spread arises primarily from variable Arabian Sea sea-breeze timing and 40–70% daytime humidity levels, which can moderate afternoon buildup by 1–2°C. Recent overnight lows near 29°C further enable daytime warming, yet strengthening coastal winds introduce the main uncertainty distinguishing the tightly clustered 35–37°C probabilities. Official PMD hourly observations at the airport station will resolve the market.