There is debate about whether one should be warm, dry and comfortable doing Qigong. Some texts and I can also attest that my late Master T.K.Shih taught that one should be warm and comfortable when performing Qigong. The reason is based on opening the pores of the skin and the gates of the body in cold, windy or damp weather could predispose one to detrimental exogenous qi deviations. In his later years Master Shih practiced qigong only inside from what he told me. Chinese Traditional Medicine texts along with many Daoist practices would also back him up on that point. Calm mind, calm environment and comfortable loose clothing is the ideal.
I have talked with other practitioners, teachers and masters and there are those that would disagree and state it was just fine to practice in non-ideal settings and temperatures. I even know of one who likes to practice during thunderstorms. In his opinion, the qi is quite powerful in the air.
Now after practicing qigong for 18 years, I can tell you from my experience that if you enjoy doing it, the rest of the factors are almost irrelevant. Other masters and instructors may disagree with me but like the 'Dude' says "It's just your opinion, Man."
Now, personally I practice a lot indoors in my den, but on a nice day, I will certainly be outside. Every now and then I do break out of my comfort zone and foray into a cold day, during a snow fall, the bitter cold of a winter night under stars or the blazing, burn inducing rays of the sun (when that happens twice a year in Michigan ). Being out in the environment always seems to give me a better feel. Sun, sky, wind, outside air, smells or grass or wet cold wood to me are added layers to the experience.
Recent research is showing exposure to outside air bathes us in more negative ions that are in the environment vs. the positive charged particles we are overly exposed to. In the stagnant air of a house that is circulated by a furnace or air conditioner along with all the positive ions produced by our electrical appliances, TVs, phones and computers, getting outside may be the best thing for us, qigong or not. Feel free to google the healthy benefits of negative ions as it is better stated throughout the internet than I can provide space for here.
Further research into exposing ourselves to the cold can have beneficial effects upon our nervous and immune systems. I am not saying one has to go all 'Wim Hof Iceman' into deep cold exposure, but I think some cold built into ones health and fitness regimn might be quite beneficial.
So if you are a tai chi, kungfu or qigong practitioner, get outside and level up your game. If its in the cold, then step up and enjoy the challenge.