Every year, the real estate market goes through busy and slow times. Usually, winter is slow, spring is crazy, summer is slow, and fall is busy until November. Weather is a factor on the winter/fall side, but the summer is often slow because people go away. Think of this as an opportunity!
You don't go away for the whole summer, right? So use those extra-long days and evenings to declutter and throw away items you no longer need. I have one friend who rents a dumpster-and fills it-every summer. A manager in our office has one storage place that she lets her husband fill up all year, and then she empties it, so that he can start over. We've all been flooded with references to "tidying up" and "finding what gives us joy". A few minutes every day, and your home will look better by fall. Have family visiting? Make them take belongings with them when they leave.
Whether you are a buyer, and cleaning up makes it easier to move, or to sell the home you are currently in, or a seller, and the same applies in the opposite order, you will do better--and feel better-if you lighten the load. Sometimes people like what's under all the stuff so much that they decide to stay where they are!
The other job best done in the warmer months is to take care of all those deferred repairs and maintenance. Again, you may enjoy living where you are, once everything is fixed. However, dealing with all the inspection items will make your eventual sale go much more smoothly. And, if you aren't leaving right away, why not give yourself the gift of an improved home in the meantime?
It's easy to be lazy at any time of year. However, most people have more time to be productive when the days last longer. Make this your year to take advantage of that extra time, and add value to your property.