British Columbia has suffered multiple record-setting summer droughts in the last decade. Historically low summer streamflows have devastated many fish populations, threatened Indigenous cultural and ceremonial uses of water, and forced the province to curtail water use for irrigation, with serious economic consequences. However, unlike other jurisdictions with similar problems, British Columbia has no seasonal streamflow drought forecast system to provide advanced warning to water managers, conservation groups, Indigenous rights-holders, and farmers of the likelihood of extreme drought conditions. _x000D_ We have developed seasonal (1 to 6 month lead time) streamflow forecast models for 207 unregulated, gauged streams in British Columbia, which predict the probability of reaching drought levels 1 through 5 in the late summer. The models assimilate real-time streamflow and snowpack data with 6-month meteorological forecasts from eight weather forecast centres around the world. We compare regression techniques that have been used for decades with Long Short-Term Memory models. For both, we find that most of the uncertainty in the hydrologic prediction derives from uncertainty in the meteorological forecasts. Forecast skill on April 1st is only marginally better than a reference (climatological) forecast but improves considerably throughout the spring and summer as the lead time decreases._x000D_ We will be disseminating forecasts on a monthly basis throughout spring and summer 2025, via an interactive web application at https://sruzzante.shinyapps.io/BC-streamflow-drought-forecast/.
