Ever wonder why the same temperature feels cooler in the Autumn than it does in the Spring? The answer lies not in your imagination, but in your skin. Over months, receptors in your skin acclimatize to the average temperature of the season: frigid weather in the winter and hot or humid weather in the summer. When those same receptors are faced with a sudden shift in temperature, they feel the difference keenly. So 11C (about 52F) may cause you to whip on a pair of shorts and a tee-shirt in February but has you bundling under blankets in October.
So if you've been resisting grabbing a warm coat the past few days, go ahead and turn on the heat while you're at it. It takes your body several weeks to get used to the new normal. Which is good, because for those of us in the Northern Hemisphere, it's just going to get colder.