Australian Shepherd

Question
I adpoted a 4 year old Australian Shepherd and he is great.  How low can the outside temperture get befor eit's too cold for him to be outside all day.  Thanks

Answer
I don't agree with putting a dog outside in a pen all day, if that's what you mean. Aussies are smart and need mental stimulation and a job to do, and they hate being isolated from their family members, so many of them will become bored, anxious, and even destructive if left alone outdoors.  In short, the dog will be unhappy, and, if alone, will likely not exercise, but will lay by the door waiting for you!  If you mean that you want to know if your dog can be out with you all day, then I think temperatures in the 40's are fine, so long as the dog isn't just lying around.  After all, their coat may insulate them, but lying on cold ground can't be pleasant on their joints as they age.
One way to keep your dog occupied when he can't be outdoors is with "interactive toys" - www.activedogtoys.com has a nice selection.  I have a "Go Dog Go" which is a tennis ball launcher that the dog learns to operate on his own, so if your dog likes balls, that would be a great way to exercise him on a slightly colder day.  I have found that some dogs still don't want to use it if you aren't there, but many will.  Good luck, and enjoy your Aussie!