diff --git a/lib/matplotlib/cm.py b/lib/matplotlib/cm.py
index 6ed13cd2f41d..081f5415ab8d 100644
--- a/lib/matplotlib/cm.py
+++ b/lib/matplotlib/cm.py
@@ -275,6 +275,13 @@ def to_rgba(self, x, alpha=None, bytes=False, norm=True):
         x = ma.asarray(x)
         if norm:
             x = self.norm(x)
+
+        np_alpha = ma.asarray(alpha)
+        if np_alpha.ndim == 1 and np_alpha.shape == x.shape:
+            rgba = self.cmap(x, bytes=bytes)
+            rgba[0:, 3] = np_alpha
+            return rgba
+
         rgba = self.cmap(x, alpha=alpha, bytes=bytes)
         return rgba
 
diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
index 5576def9d440..7855f69ff404 100644
--- a/lib/matplotlib/collections.py
+++ b/lib/matplotlib/collections.py
@@ -678,6 +678,11 @@ def set_alpha(self, alpha):
         ACCEPTS: float or None
         """
         if alpha is not None:
+            # Check if alpha is an array of matching size
+            np_alpha = ma.asarray(alpha)
+            if np_alpha.ndim == 1:
+                artist.Artist.set_alpha(self, np_alpha)
+                return
             try:
                 float(alpha)
             except TypeError: