The Seasonal outlook basin overview layer shows the maximum area-averaged probability of unusually high (> 80th percentile, blue) or low (<20th percentile, orange) weekly river flow occurring during the four 4-month forecast horizon for 305 major world river basins, using colour-coded cetagories:

  • Dark blue: > 90% probability of high flows
  • Medium blue: 75-90% probability of high flows
  • Light blue: 50-75% probability of high flows
  • White: Near normal flow (below 50% for both low and high flow)
  • Light orange: 50-75% probability of low flows
  • Medium blue: 75-90% probability of low flows
  • Dark blue: > 90% probability of low flows