Add conversion of dtype to threshold handling (fixes #136)

climix/index_functions/support.py

@@ -79,6 +79,9 @@ class ThresholdMixin:
 
     def prepare(self, input_cube):
         threshold = self.threshold
+        threshold.points = threshold.points.astype(input_cube.dtype)
+        if threshold.has_bounds():
+            threshold.bounds = threshold.bounds.astype(input_cube.dtype)
         change_units(threshold,
                      input_cube.units,
                      input_cube.standard_name)