I've shot the hell out of a second generation G22, -40 won't hurt it. I've left it in the garage for weeks on end in the cold to test it in cold weather. I've tried it in +40C heat too. I've also thrown it into muck puddles at the range (you should see the look on the face of 1911 shooters.....), slapped mags in it and its fired fine. I've tried limp wristing it in cold weather, packed full of mud, gravel, sand etc and have not expierenced a failure to fire, extract or feed. Apart from a face full of muck when pulling the trigger, nothing much seems to slow it down. Check out some of the Glock torture tests, I've tried some of the same tests and my original G22 passed with flying colours. It was these tests that sold me on the design, and Glock is the only pistol I will trust in a truely brutal situation like heat, cold, mud, sand etc. I've fired 200+ rounds rapid fire in cold weather, hot weather and dunked the gun into a bucket of water when it was steaming hot, them shot it again. Kept on firing. Freeze a Glock in a bucket of water, done it, didn't hurt it.
Aside from making sure the barrel was clear, the rest of the pistol was so packed with mud and much you would swear it wouldn't function. It is truely a great design IMO. As a side note, the tennifer finish held up great, barely any scratches on the slide and the polymer frame was unaffected, apart from the odd ding mark.
I did these tests in 1995, no idea if the third generation Glocks are as tough, but I assume them to be.