The skinny on what temperature is best for playing strings outdoors

Most of you already know that the piano quartet at the Inauguration ceremony last week used a recording because the temperature was so cold. Well, what are the best conditions for playing outdoors. Slate magazine's Explainer (Brian Palmer) recently tackled this issue here. The following quote from that article gives you the skinny on the topic:

What are the optimal climatic conditions for playing an instrument?

Around 70 degrees, with 40 percent to 50 percent humidity. But instruments are more stressed by rapidly changing conditions than by extreme temperatures or moisture levels. Because heating systems warm air without adding moisture, the relative humidity is often as much as 30 percent to 40 percent lower indoors, even on a cold and dry day. When instruments made of wood move between environments of varying humidity, they absorb or expel moisture. The resulting expansion and contraction can crack the instrument. String instruments, such as violins and cellos, are particularly susceptible to cracking, because they are often made of two different types of wood (usually spruce and maple) that absorb moisture at different rates. Hide glue, the collagen-based sealant used to secure the pieces together, moderates the problem. It is weaker than synthetic glues and is likely to release the various parts before the wood cracks.