I guess it is a matter of individual prefernce. If I hit a deer and signs are present that indicate that the hit may be mortal, and it starts to rain and rain is forecast for the next day, I am going to start tracking very soon but I won' t push hard.

As Matt said, the blood is not going to dissipate so rapidly you cannot find any blood in rain. In fact, moisture will often expand the blood drops before the blood is completely washed away. As Matt also said, trees, brush, etc, is going to protect the blood until the area is completely drenched.

dabowhunter:

I do not know about why other readers recommended getting on the trail rather than wait, but I will tell you why I would.

Visual searching just for the deer is not as productive as having signs to also follow e.g., blood, tracks, slides, falls, etc. If it is going to rain all night and the next day, most of the signs will be obliterated or completely gone. If the deer is hurt bad, he is going to harbor up in deep cover.

Regardless that you might be getting on a track earlier than usual, in the described situation I am going to try to determine a direction of travel before any signs that may have been present disappears and now I can only look for the carcass. While doing so, maybe I will also find additional signs that indicate how bad he is hit.

Of course, that is what I would do, not what everyone should do.