From 9d1c3cb5d7fba68c0dc675dd80825cac8b644e01 Mon Sep 17 00:00:00 2001
From: Keewis <keewis@posteo.de>
Date: Sat, 6 Mar 2021 23:16:57 +0100
Subject: [PATCH 1/3] duplicate the level if a single level was passed

---
 xarray/plot/utils.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xarray/plot/utils.py b/xarray/plot/utils.py
index 5510cf7f21..57cdf9f45d 100644
--- a/xarray/plot/utils.py
+++ b/xarray/plot/utils.py
@@ -60,6 +60,11 @@ def _build_discrete_cmap(cmap, levels, extend, filled):
     """
     import matplotlib as mpl
 
+    if isinstance(levels, (int, float)):
+        levels = [levels, levels]
+    elif len(levels) == 1:
+        levels = [levels[0], levels[0]]
+
     if not filled:
         # non-filled contour plots
         extend = "max"

From 7977ce0fa25971abc50a5dd010d15d71f8013a84 Mon Sep 17 00:00:00 2001
From: Keewis <keewis@posteo.de>
Date: Sat, 6 Mar 2021 23:29:39 +0100
Subject: [PATCH 2/3] don't handle scalars

it seems these will never be passed at that level
---
 xarray/plot/utils.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/xarray/plot/utils.py b/xarray/plot/utils.py
index 57cdf9f45d..a83bc28e27 100644
--- a/xarray/plot/utils.py
+++ b/xarray/plot/utils.py
@@ -60,9 +60,7 @@ def _build_discrete_cmap(cmap, levels, extend, filled):
     """
     import matplotlib as mpl
 
-    if isinstance(levels, (int, float)):
-        levels = [levels, levels]
-    elif len(levels) == 1:
+    if len(levels) == 1:
         levels = [levels[0], levels[0]]
 
     if not filled: