Well, if you are fortunate enough to have a gym near you and can afford the monthly installments, then it might be life in the treadmill for a couple months. Some people loathe the treadmill or "dreadmill" for various reasons: lack of scenery, sense of running and not going anywhere or plain and simply put "it just doesn't compare to the feeling of an outdoor jaunt." But maybe this is your chance to mix it up. If you have never run speed intervals, this could be a great place to try them out. Most treadmills have distance and speed displays so why not try doing some variation of a speed interval? This is perfect if you don't like being at the gym for extended periods if time since you can keep the time short, but get a good workout when the weather isn't cooperating. Various intervals (link) can be easily tracked on the treadmill. This is also a great chance to work in some cross training on your non-running days. Hop on the bike, elliptical, or try a core workout to strengthen your running form.
If the gym isn't possible (weather permitting) lunch runs are always a possibility. With a 60 min lunch break, factor in 10 min to change before and after leaving you 40 mins which could be a 20-30 minute run and 10-20 mins to eat. If a shower is not available at work (probably for the majority) then baby wipes are always helpful. Here is a link from Runner's World that also has some great tips for mid-day runs. .
But I agree, nothing beats the open outdoors and getting in some serious miles under your belt. Over the weekend it was around 40 degrees in San Francisco and I was scheduled to run 10 miles. I had little sleep and with the cold, I was not looking forward to the run. If there was a magic time machine I probably would have wound back time and stayed in bed. But fortunately there was no such thing so I ended up running 12 miles... that's right 2 more than I was originally scheduled to run and it was fantastic. Afterwards, I was glad that I woke up early and got in my morning run. My legs were stiff and I was cold when we originally started, but about 10 minutes in I was nice and warm and starting to break a sweat. After that it was clear sailing. Sometimes the right attire to stay comfortable in cold weather is all you need to get out there. After that let your love of running handle the rest. Once you get going, you'll be glad you're out there.
Of course that is easily said since we don't get snow in the Bay Area. For those of you in colder weather or the snow, my thoughts are with you... Feel free to share your advice or experiences in the comments.