Once you flip the calendar to "spring" months, that's the best time to have your pool installed, right? Maybe not. Spring, traditionally, is the rainy season for many areas of the country and this makes the ground sometimes too wet for excavation. Soggy dirt will make the excavation difficult and cause the dirt to collapse in on itself and wet ground can be rough on heavy equipment.
And in the spring time, pool contractors have already likely seen their construction calendars fill up for the coming installation season.
The best time of year to think about pool installation is in the pre-winter drier months of the year. It's best to think about having your pool installed before winter. Another factor to consider it price it's less expensive to have a pool installed once pool season isn't in full swing because pool contractors aren't as busy and are looking for work. You might be able to negotiate for a better price and the work might be done more quickly as you won't be on a waiting list. True, if you live in an area of the country that doesn't see a lot of rain in the spring -- the deserts of Arizona for example, you can still consider a spring install but you might want to contact a contractor before the building season to make sure you don't miss out.
If you have your pool installed off season, it will be ready and available for your family once the warm summer, swimming season kicks into high gear.