Actually, the OAT is irrelevant. What is relevant is whether or not there is frozen contamination adhering to the critical surfaces. And if there is, is it allowed for takeoff. Typically, airliners can have certain amounts of frost on the bottom of the wing. At least one 737NG airline can have frost in certain areas on the upper surface of the wing. The first case has to do with cold fuel causing frost to form, frequently at an OAT above freezing.
So in the case of the original question, it is possible on some aircraft to have rain/drizzle freeze on top of a wing where it is affected by cold fuel. Some aircraft such as the MD-80 are more vulnerable to this than others.
So what to do. A visual check can help but clear ice can be difficult to detect, especially on a wet wing. Trained maintenance is the best answer for actually getting a tactile check. A pilot may be able to as well but it could be at risk of some sort of falling injury due to lack of proper equipment.
Knowledge and experience on type is useful for deciding how likely this is and when to check and how vulnerable your aircraft is to damage from pieces of ice if you do takeoff without a proper check.
Aside from that, there is little other risk in terms of critical surface contamination at the OAT originally mentioned.
As an aside, watch out for freezing fog causing ice buildup on propellers.