In the Northeast/New England region, we have been getting a few warmer days, but not nearly hot enough yet to turn on the AC. You could just put on a fan or two to get a good breeze going, but there is another option as well. Many houses have the furnace in the basement/cellar and it is almost always cooler down there. Most of the duct work connections on those basement furnaces have a service vent or removeable section of ductwork that opens to the basement air space. If you have a way to turn on your furnace fan (at the thermostat or with a switch near the furnace) you can cool your house with basement air. You need only block the cold air returns on the first floor with a piece of cardboard or plastic and open that service vent in the basement. Now when you turn on the furnace fan, you will circulate cooler air from the basement to the other floors of the house.
Hope this idea helps you out for these in-between days that are neither too cold or too hot yet still not quite comfortable.
Thanks,
-Joe