Boost your immunity:- It’s actually not possible to completely make yourself immune to the seasonal changes. But taking few steps can definitely support your immune system and helps you in staying healthy during various seasons
Healthy diet:-
Always consume a balanced diet and nutritious diet rich in foods veggies lean proteins and healthy fats
Include sources of healthy fats such as avocados, nuts, seeds, olive oil, and fatty fish (like salmon) for omega-3 fatty acids.
These provide all essential nutrients that support your immune system and your overall health
Regular exercise:-
Engage in regular physical activity to boost your immune system and overall health. Physical activity increases blood flow which helps immune cells move freely through throughout body allowing them to detect and respond to infectious more effectively. 
Physical activity increases white blood cells and antibodies. It increase immune cell activity their production and circulation. Physical activity reduces stress hormone.
Physical activity also helps in regulating hormones that affect immune health. 
Physical activities like cardiovascular exercises help in lungs function. Brisk walking and jogging are cardiovascular exercises.
It is very important to note that while moderate exercise can boost the immune system, excessive intense exercise without proper rest and recovery can suppress it, finding a balance between regular physical activity and allowing the body to rest is a key. 
Exercise maintains weight which can positively impact immune function while obesity weakens immune system.
A healthy gut microbiome is linked to a stronger immune system. Exercise increases balanced microbiome. 
The bacteria in the microbiome helps digest our food, regulate our immune system, protect against other bacteria that cause disease, and produce vitamins including B vitamins B12, thiamine and riboflavin, and Vitamin K, needed for blood coagulation.
Sleep:-
Better physical activity leads to better sleep which is essential for immune system. During sleep body produces immune system supporting substances.