Miami’s climate is classified as tropical monsoon, with hot, humid summers and warm winters. (Wikipedia: Climate of Miami)
During the wet season (May to October), daytime highs are typically in the mid-80s to mid-90s °F (29-35 °C), with frequent afternoon thunderstorms and high humidity.
Hotels in neighborhoods like Miami Beach, downtown, Coconut Grove, or near highways are good bets. Because match dates will cause high demand, book lodging well in advance. Parking near the stadium will likely require pre-purchased passes. Use park-and-ride, shuttle services, or transit when available to reduce traffic hassles.
Miami is a major metropolitan area with both safe and riskier districts. Standard precautions: avoid isolated or poorly lit areas at night, travel in groups, secure valuables, and choose lodging in well-trafficked, stable neighborhoods.