Mujitsu and Tairaku's Shakuhachi BBQ

I'm posting this in the flutemaking section, as I suspect builders will likely have some insight on the topic. My apologies if it belongs in a different area on the forum.

I like to keep a flute in the car when I'm on the go, I often have a little time here and there during the work day to grab some extra practice. What is the "safe range" where temperature is concerned? I have a yuu for the more extreme times of the year, but it certainly isn't my preferred instrument.