50°F is the accepted minimum temperature for corn germination but other factors are in play when deciding if planting into low 50’s or colder soil is the right decision. 

• How comfortable are you having seed lay in the ground for an extended period? It takes 100-120 GDU for a corn seedling to emerge from the soil. This means corn planted into soils ranging 50-55°F could take 3 weeks to emerge while corn planted into 60°F soils could emerge in 10-12 days.
• What is the short-term and long-term weather forecast? If there is a warming trend on its way, then planting into cooler soil may be more acceptable.  But is a cold and/or wet spell being forecasted?  It may a good choice to wait for a warming trend to plant as imbibitional chilling injury becomes a concern.  This injury can cause delays in emergence, irregular plant growth, or failure to emerge.  A great resource for this information can be found at advantageacre.com where the Weather Timeline can give you a nice outlook on upcoming weather trends.   
• What is the seed treatment being used? Is your selected treatment designed to protect the seed/seedling throughout a delayed germination/emergence period as well as the early stages of the corn seedling’s growth?

Consider these factors while making the decision to plant into cool/wet soils.  It will help you determine the risk acceptable to you and adjust your plan if necessary.