If the selling of ice cream was found correlated (0.4-0.6) to the temperature, can we conclude that ice cream selling "is related" to the temperature? Or we can just say that there is a relationship?

By using is related, do you imply cause and effect relationship? Can we also say that other factors do exist. For example, the price of ice cream is lower in summer when the temperature is high, so the selling is also high.