diff --git a/src/seismic_hazard_forecasting.py b/src/seismic_hazard_forecasting.py
index 806ca6c..e41d787 100644
--- a/src/seismic_hazard_forecasting.py
+++ b/src/seismic_hazard_forecasting.py
@@ -339,6 +339,12 @@ verbose: {verbose}")
         elif time_unit == 'years':
             multiplicator = 1 / 365
 
+        # Raise an exception when time_range from the user is too large
+        if time_range/multiplicator > 0.5*(time[-1] - time[0]):
+            msg = "Activity rate estimation time window must be less than half the catalog length. Use a shorter time window."
+            logger.error(msg)
+            raise Exception(msg)
+
         # Selects dates in datenum format and procceeds to forecast value
         start_date = datenum_data[-1] - (2 * time_win_duration / multiplicator)
         dates_calc = [date for date in datenum_data if start_date <= date <= datenum_data[-1]]