I do a lot of stain work and I would wait three to four weeks if possible to stain after purchase. Keep in a dry, weather proof area if possible-a garage, shed or workshop. If you have to keep the lumber outside, elevate it on some 4 x 4 runners and expose it on clear days.
Scientists say that solutions are homogenous systems. Everything in a solution is evenly spread out and thoroughly mixed. Heterogeneous mixtures have a little more of one thing (higher concentration) in one part of the system when compared to another. Let's compare sugar in water (H 2 O) to sand in water. Sugar dissolves and is spread throughout the glass of water. The sand sinks to the bottom. The sugar-water is a homogenous mixture while the sand-water is a heterogeneous mixture. Both are mixtures, but only the sugar-water can also be called a solution. Pretty much. Solutions can be solids dissolved in liquids.
Vinegar and oil salad dressing is heterogeneous since two liquid layers are present, as well as solids. Air with clouds is heterogenous, as the clouds contain tiny droplets of liquuid water. SOLUTIONS are homogeneous mixtures.