Water is not exactly a great friend as far as wood is concerned. The moisture makes the material rot and warp or at times even mold can grow. If there has been a rainstorm then it is natural for water to seep into the boards through even the tiniest of cracks. The holes made with screws or nails also are sufficient for the water to seep in. Now, if the water is not dried up immediately after the storm dies; there is liable to be damage to the deck. It is true that there are different types of materials and some can resist water more than other; however wooden decking as a rule should be resealed every year or every couple of years.
The next thing is to check the extent of water damage. If it is noticed that there are water beads then there is no need to panic but if it seems that the floor is absorbing water then an immediate action should be taken. Sealant should be applied or certain bards may need replacement; however it is better if a professional is called in to take a proper look and assess the damage.
Long term exposure to sun is also a cause for deterioration of the deck. The color fades, boards get dried and warped and even cracks at various places. A brightening solution is available at most hardware stores to bring the cheer back to the floor. There are various products available for application that keeps out the UV rays from penetrating.
Another enemy of wood is frequent change in temperature that results in cracks and breaks. Only regular inspection will make it evident and popped out nails and damaged boards can be replaced or it might prove dangerous too.