Hello lybrate-user,
Having fatigue and mild fever like symptoms are common during sudden change in the weather. To avoid falling ill, you can opt for the following things:
1. Exercise daily
2. Have a good balanced diet with proper balance of proteins, vitamins, minerals, fibres
3. Have some vitamin D
4. Keep yourself hydrated
5. For weak immunity, you can start having Herbofit daily after breakfast or with a glass of milk. Herbofit from Dr. Vaidya's. HERBOfit takes the 21 active ingredients of Chyawanprash and puts it in a capsule form. HERBOfit is a healthier, tasteless and more convenient way to consume Chyawanprash for the modern consume.
Hope this helps!