And if you have asthma it's bad even below 0 C. I use my Lungplus [1] as soon as the weather hits +5 C, makes me able to actually do something outdoors in the winter. It's just a heat exchanger in your mounth, storing heat from the exhaust air, and heating up the intake air [2] :-)

[1] https://www.lungplus.se/databl_e.html

[2] https://duckduckgo.com/?t=ffab&q=lungplus&iax=images&ia=imag...