Data is updated every 15 minutes and plots with the latest 15 minute increment on the far right of the graph. The graph shows the most recent 96 hours (or 4 days) worth of data. Every 15 minutes, the data 'shifts' left with the oldest 15 minute increment falling off the left & a new 15 minute incremental reading on the right. Click any 'graph' button on the left side panel to see that station's graph. Hover mouse over any column on the graph for detailed reading. Status on left side panel is real time status based on when you loaded the page, refresh page to get updated real time status.