The New York Times has a tool on their site which allows you to check how much warmer a city was in 2018, compared to an average calculated using data from 1981 to 2010. The data, provided by AccuWeather, comes from a database of more than 3800 cities worldwide which shows that about 83% of cities experienced average temperatures higher than normal last year.
NASA and NOAA both determined that 2018 was the fourth warmest year on record, and that December 2018 was the second warmest December in the 139 year record. See this article for more information.
