New Jersey’s housing market appears to be heating up into the spring with some counties seeing homes sell within a month, the latest data from Realtor.com shows. Homes in Somerset, Morris, Union and Essex all saw homes sell within a median of 31 days in February. Homes in Salem County remained on the market the longest at 81 days. Statewide the median time on the market for homes in New Jersey was 39 days in February. Nationwide, homes sold within a median of 61 days, the data showed. A note about the data: Realtor.com calculates time on market by taking the median number of days properties ar…