The best food to enhance the immunity is the healthy will balanced diet containing food rich in vitamin c which is : broccoli ، green pepper, tomato, orange , strawberry

Also ginger , garlic and Curcuma to be added with cocked food

No particular foods will 'protect' against cold beyond those that normally boost immunity in normal temperatures. The key is ensuring adequate healthy diet, identifying which foods or nutrients are likely to fall short. But some would argue potentially increasing calories and fat if the cold period is long. That is a normal response to cold across all cultures and throughout history.

Nutrition, immunity, and performance in extreme environmental conditions have been comprehensively studied for decades. Man is an especially adaptive organism, but some dietary considerations must be met. The literature is remarkably rich in the details of humans' dietary micronutrients, macronutrients, and energy requirements in cold conditions. The following examples of resources may be helpful [1-4].

References:

[1] Gombart AF, Pierre A, Maggini S. A review of micronutrients and the immune system–working in harmony to reduce the risk of infection. Nutrients; 2020, 12, 236. doi:10.3390/nu12010236.

[2] Marriott BM, Carlson SJ. Nutritional needs in cold and high-altitude environments: applications for military personnel in field operations. Committee on Military Nutrition Research, Institute of Medicine. The National Academies Press, 1996. http://www.nap.edu/catalog/5197.html.

[3] Wolinsky I, Hickson JF. Nutrition in exercise and sport. CRC Press, 1994. https://apps.dtic.mil/dtic/tr/fulltext/u2/a275621.pdf.

[4] Srivastava KK, Kumar R. Human nutrition in cold and high terrestrial altitudes. International Journal of Biometeorology 1992; 36, 10–13. https://doi.org/10.1007/BF01208728.

I will suggest a continued balance of nutrients but a slight increase in carbs and quality oils for heat.