ISH is a global database, though the best spatial coverage is evident in North America, Europe, Australia, and parts of Asia. Coverage in the Northern Hemisphere is better than the Southern Hemisphere. Figure 1 shows the spatial distribution of ISD stations for all time periods. The overall period of record is currently 1901 to present. Figure 2 shows the number of stations per year. Some stations have over 50 years of continuous reporting during the latter half of that time period. However, many stations have "breaks" in the period of record (eg, 40 years of data may be spread over a 70-year period). Efforts are well underway to integrate additional data sources into ISD, which will provide for more U.S. data prior to 1950 and some data prior to 1900. Also, plans are in place to gradually integrate datasets provided by various countries to increase data coverage and periods of record for some areas.