With the weather turning a bit more inclement, it is time to think realistically about your gear and clothing for the elements.
Actually you should think about this year round, summer is as dangerous as the winter months. In fact, regulation of the body's core temperature is one of the most important facets to keeping your butt alive. Cody Lundin addresses this in his book "98.6 Degrees: The Art of Keeping your Ass Alive". Having certain items with you, in your kit, and keeping a positive attitude will help you keep your butt alive when that day hike goes awry.
One very good point that Lundin makes is 1) having a plan and 2) letting people know what your plan is. That really boils down to letting someone know where you are going, what route you are taking, and when to expect you back.
I've been doing this better. I write down where I am parking, and what trail I am going to run. I then also give my husband a ballpark time when I will return. As in " don't send out the search party until 5 pm". When I get to wherever I am parking, I put a slip under my windshield wiper with what trail I am travelling, and also my husband's name and home phone number. I feel safer leaving that info, knowing the park rangers will have a contact number if the vehicle is still there late in the evening.
I've also made sure I have a few essential items in my hydration vest: albuterol inhaler, emergency whistle, a Bic-type lighter. These don't weigh much, so they are always in there. There are usually a few Hammer espresso gels which just stay in there, even for a short run. According to Lundin, it's these short day hikes that people don't take the water bottle, or leave the sweater in the car, where problems can occur. I'm getting better about checking the contents of the hydration vest too! to make sure these items are there. One other item I should add, which is also little weight, is an emergency blanket, one of those mylar sheets.
Think about what you are doing before you run out the door for just a "short run in the woods". Tell someone where you are going (even for a road run, sometimes cars are just as dangerous!) and when to expect you back. Tell them the route so they can start looking when your time has expired-before you do!!