Cooling weather may have caused increased COVID-19 spread. Considered across many regions, the average reproduction number (R) gradually increased from ~1.0 to ~1.2 as daily high temperatures fell from >27 °C to ~10-15 °C (>80 °F to 50-60 °F). Other factors, including decreases in sunlight and/or UV exposure, may have slightly increased this further.
Warming weather is unlikely to stop the spread of the pandemic. Warm, sunny weather may have some limited impact on the rate of spread, but in the absence of strong interventions, the pandemic is likely to continue spreading through the summer months in most parts of the world.