There are a few key factors that separate the average runners from the good and the good from the great.

Training, mental strength, diet, Consistency, etc.

The one thing that always irks me is when I hear people say they ran 5 or 10 miles on the treadmill because of the weather. The only weather condition where you should be running inside is lightning and thundering. Besides that you need to be outside. 

You need to train your body to be prepared for any condition: snow, sleet, rain, heat, cold, wind, etc. 

You need to be prepared to run in those conditions. That’s what will separate from the pack. No matter the weather you will be prepared. This will give you a huge leg up on your competition. It will make you mentally stronger, never caught off guard, and excited to run in bad conditions. While others will be complaining of the weather you’ll be licking your chops. You’ll know you’re ready no matter what. 

Run outside. It’s worth it.