I use UPS for shipping and just check their website. They have a page that states whether or not they are experiencing delays. However, it doesn’t always predict delays ahead of time. For that, I simply use weather.com and monitor the weather in Louisville, Kentucky. The main UPS hub for North America is in Louisville and basically everything that I ship goes through there. My general rule of thumb is that if it’s cold, it’s still okay to ship (this is absolutely dependent on how you pack, but I’m personally not worried about cold weather), but if there’s any ice/snow forecasted then it’s a no go. That’s typically when planes get grounded and boxes end up delayed.
That said, I’m not shipping today and may not be at all this week due to icy conditions in Louisville, starting tonight.