What happens if I exceed the Photon's min temp or max humidity?

I’m planning on building a remote weather station using my Particle Photon and a BME280. I live in Toronto where it occasionally drops below -20°C in the winter, but I noticed the Photon’s recommended minimum is exactly -20°C. What are some of the things that can happen if I exceed that temperature? Is the cold more likely to create temporary problems, and less likely to create permanent unfixable damage?

How about the humidity? It can get very warm in Toronto’s summer (+35°C sometimes), and combined with a rain, can make the air extremely humid. Dew sometimes forms on the grass in the mornings. Sometimes there’s fog. The photon uses very small circuitry compared to a traditional Arduino, and the package under the square metal shield looks extremely sensitive. Is it safe (in terms of permanent damage) to leave the photon exposed to the air (but not direct rain) in these conditions?