Toronto experiences variable spring weather in mid-April, with typical highs ranging from 8°C to 15°C. A high of 21°C would represent above-normal warmth, requiring an unusual warm air mass to move into the region. The current market odds of 3% YES reflect trader expectations for below-normal to near-normal temperatures on April 18, consistent with historical seasonal patterns and recent meteorological forecasts indicating cooler conditions in mid-April. This market resolves at midnight UTC when Environment Canada publishes Toronto's highest recorded temperature for the day, making the outcome definitively measurable. The 21°C threshold is meaningful because it represents a significant departure from April's seasonal norm, making such temperatures relatively uncommon despite occurring occasionally when warm weather systems migrate northward from the US. The market has accumulated $1752 in trading volume over 24 hours with $1353 in available liquidity, providing reasonable execution depth for traders. Odds may shift materially as the resolution date approaches if forecast models update to signal warmer conditions moving into the region.