Just like preventative maintenance on your car, if you take care of a few small items around the house every week, you can avoid many emergency breakdowns and expensive repairs.
If you are finally admitting you are into Spring, it is time to turn off Winter. The very first thing you can turn off, clean up and close off for the summer is that humidifier. If it is a free standing humidifier, clean it up and put it in storage. If it is a humidifier attached to the furnace you actually have some more important stuff to do.
You must turn off the water to the humidifier, otherwise it will just sit there and go stagnant over the summer. If you have air conditioning connected to your forced air furnace, it is critically important that you close the damper between the humidifier and the furnace ducting. If you do not do this, you will create an air flow around the air conditioner condensing coil that will end up freezing up the whole device. This could cause damage to your compressor. If you don't know how to do this, or can't find the damper, you must bring in a professional to install the proper damper for you. For more information on humidity and humidifiers, check the SEARCH tab above for "Humidity".
Once you are sure that you don't need that furnace any more, you should turn off that gas pilot light. That will save you money over the summer. Check out "Pilot" in the SEARCH tab above.
Probably the one outdoor structure that takes the most beating from the winter is your fence. It should be the first thing you tend to as you get into the yard. See if it has heaved or shifted with the frost. Are all the boards in good condition? Does the gate close properly or do you need to adjust the latch? Some clay soils heave with the thawing of winter and then settle back down once full drainage has been restored by the ground warming up; so if you know this to be the case with your house you may want to wait before doing any major work on that gate. Of course you need to evaluate if it is time to re-stain or re-paint the fence once the structure has been solidified. Check the SEARCH tab above for more information on "Fences".