Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Oklahoma City to Düsseldorf as you normally would.
In terms of precipitation, rainfall in Düsseldorf ranges from 1.2 - 3.1 inches per month. July is typically the wettest month, when rainfall can reach 3.1 in. March is typically the driest time to visit Düsseldorf when rainfall is around 1.2 in.
If weather is an important factor for your trip to Düsseldorf, use this chart to help with planning. For those seeking warmer temperatures, August is the ideal time of year to visit, when temperatures reach an average of 64.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 33.8 F).