Depending on site conditions, we would recommend an acclimatisation time of 7 days.
According to the Floor Square website:
Try to bring the flooring into your space approximately a week in advance to let the wood acclimate to its environment.
while the Ask Jeeves website states:
A hardwood floor ideally needs at least 72 hours to adjust to the room temperature of the home into which it will be installed. Your contractor may drop off the materials 3 or more days in advance to accomplish this.
The Hardwood4less website states:
Between 5 and 10 days ahead of time, check to see if the temperature and humidity of the space is at normal living conditions. In other words, let the heat or air run as it would normally for at least 5 days.
The Gaylord Hardwood Flooring website states:
Flooring should be delivered to the job site up to two weeks before installation. Keep in mind that if the flooring is delivered on a damp or rainy day you may need several more days for the floor to acclimatize.
The Armstrong website states:
To acclimate hardwood flooring, move the packaged boards into the room where they will be installed and let them sit for several days, with the cartons open and raised off the ground. This allows the moisture content of the wood to adjust to the conditions in the room. Armstrong recommends acclimation for all their solid hardwood flooring products. It is not necessary to acclimate engineered wood flooring.