1 You are more likely to get injured
During cold temperatures muscles become rigid and stiff. A sudden movement can result in muscle damage or injury if warming up wasn't done properly.
2 Your body warms up slowly
In cold temperature the body warms up slowly thus extra energy and time are needed to get the body to warm up.
3 Your body cools down fast
The body cools down fast in cold temperatures. While this can help the body maintain its ideal temperature it can also result in a reduced performance as the body goes back to the pre-warming up state.
4 Less toxins leave your body
When a person sweats toxins and harmful materials leave his body. Exercising with Air conditioner on results in less sweating and as a result less toxins leave the body.
5 You feel sleepy
A very cold temperature can make a person feel sleepy and make it harder for him to warm up. When the body gets cold it reduces the activity level to help preserve energy (See also how to sleep well at night).
6 A low temperature makes the body less active
A low temperature can make a person less active and sleepy. While a very hot temperature can affect performance in a bad way a cold temperature might prevent a person from exercising well.
7 Hot weather increases heart rate
Exercising in hot weather increases heart rate. When the heart rate increases the person becomes more active. Some Pre-workouts make people more active by increasing the heart rate. An effect that can be naturally achieved by turning off the air conditioner.
8 High temperature lowers blood pressure
When the temperature gets high the blood pressure is lowered. The opposite happens when the temperature is lowered.
9 Sweating gives a feeling of satisfaction
Sweating gives a psychological feeling of satisfaction. While more sweat doesn't necessary mean that more calories are burned still sweating can psychologically make a person think that he exercised well.
10 A sudden drop in body temperature signals sleeping time
If a person came from a hot area to a place where the air conditioner is adjusted to a cold temperature then the sudden drop in temperature might signal that body that sleeping time has came making the person less active. This is why a warm bath helps people sleep.