If you work out in a gym, you can do it all year round. There is no best point.

As for the influence of environment on fitness:

Too strong sunlight will damage people's skin, and the thermal radiation of sunlight will also accelerate metabolism, so we should pay attention to prevent dehydration.

In an environment with excessive humidity, the heat dissipation mechanism of the human body will be inhibited and it is easy to get tired and suffer from heatstroke.

In cold environment, muscle viscosity increases, ductility and elasticity decrease, and working ability decreases, which is more likely to cause sports injuries. So do enough warm-up exercises before exercise.

In the park before the sun rises, the concentration of carbon dioxide in the air is the highest because of the causal relationship between the respiration of plants and the photosynthesis that does not work all night. This time is not suitable for people with poor cardiopulmonary ability to exercise.

Fitness is a career, there is no best fitness time, only those who will seize the fitness time best.