The climate of the continental or 'lower 48' states of the United States varies due to differences in latitude and geographic features such as different mountain systems in the east and the west and deserts and the great plains. Many areas to the west of the 100th meridian are semi-arid to arid, while the far southwest is largely classified as desert. While east of the 100th meridian, the climate can be humid continental in the northern areas (locations above 40 north latitude), to humid temperate in the central and middle Atlantic coast regions, to humid subtropical in the Gulf and south Atlantic regions. The southern tip of Florida is tropical. Alpine climates can be found at the higher-elevations of the Rocky Mountains, the Wasatch and Bighorn mountain ranges, the Sierra Nevada, and the Cascade Ranges of the west. The coast of California is Mediterranean, while coastal Oregon and Washington are cool temperate oceanic. There are strong seasonal changes in many parts with warm and moist summers in the east being replaced by potentially cold and slightly drier winters. In the west the storm track emanating from the Pacific Ocean is highly influential for winter weather while the inter mountain region is monsoonal with moisture and convective storms prevalent in the summer months.
The entire country can be affected by ENSO events and sub seasonal and seasonal forecasts can be very useful across numerous sectors. The outputs generated by ExtendWeather are at a 4 kilometer resolution and are updated on an approximately ten day cycle.