Phoenix, Arizona, with First +45°C (113°F) of the Year, Denver to Hit +38°C (100°F)

Marek Kučera June 16, 2025 2 min read

The southwestern United States is experiencing a significant heat surge as Phoenix, Arizona, records its first blistering temperature above 45°C (113°F) this year. Meanwhile, Denver, Colorado, is forecasted to reach a sweltering +38°C (100°F), marking an early and intense start to the summer heat season across the region.

Phoenix: Breaking the 45°C Mark

Phoenix saw its mercury climb past 45°C on Monday, June 16, 2025, signaling a strong heatwave sweeping through Arizona. This temperature is notable as it represents the first time this year the city has reached such extreme heat, a benchmark that often tests the limits of local infrastructure and public health systems.

Residents were advised to take precautions against heat-related illnesses, stay hydrated, and avoid prolonged outdoor activities during peak afternoon hours. The extreme heat can strain power grids due to increased air conditioning use and poses a significant risk to vulnerable populations such as the elderly and young children.

Denver Nearing 38°C (100°F)

Meanwhile, Denver is on track to hit +38°C (100°F), a threshold that is relatively rare for this city at this point in the year. This early heat surge is unusual for the region and has prompted local authorities to prepare for potential heat emergencies, especially given that many residents may not yet be acclimated to such high temperatures.

The rapid warming raises concerns about wildfire risks, drought conditions, and public health, as heatwaves can exacerbate these issues.

Causes and Outlook

Meteorologists attribute the heat spike to a strong high-pressure system parked over the southwestern United States, creating clear skies and prolonged sunshine. This weather pattern allows temperatures to soar, especially in desert areas like Phoenix.

The National Weather Service forecasts continued above-average temperatures for the coming week, with potential heatwaves extending further into neighboring states.

Public Safety Tips

Officials remind the public to:

Drink plenty of water and avoid alcohol or caffeine.
Stay indoors during the hottest parts of the day.
Check on neighbors, especially the elderly or those with medical conditions.
Use sunscreen and wear light, breathable clothing.
Never leave children or pets unattended in vehicles.

Conclusion

As Phoenix marks the first +45°C day of 2025, and Denver approaches the century mark, residents across the Southwest should prepare for a challenging and potentially hazardous summer. Staying informed and taking preventive measures can reduce health risks during this period of extreme heat.