diff --git a/source/_static/custom.css b/source/_static/custom.css
index d01f1e6..07cd728 100644
--- a/source/_static/custom.css
+++ b/source/_static/custom.css
@@ -116,6 +116,7 @@ img.screenshot {
 */
 :root {
     --mainNavColor: #986196;
+    --notificationBannerColor: #986196;
 }
 
 /*
diff --git a/source/conf.py b/source/conf.py
index 8c305e1..3adc08b 100644
--- a/source/conf.py
+++ b/source/conf.py
@@ -51,6 +51,30 @@
 #    "globaltoc_collapse": False
 #}
 
+# Scheduled Cosma down times
+import datetime as dt
+downtimes = (
+    dt.date(2026, 6,  1),
+    dt.date(2026, 10, 5),
+    dt.date(2027, 2,  1),
+)
+next_downtime = None
+for downtime in downtimes:
+    nr_days = (downtime - dt.date.today()).days
+    if nr_days < 21 and nr_days > -4:
+        next_downtime = downtime
+        break
+if next_downtime:
+    start_date = downtime.strftime("%d %B")
+    end_date   = (downtime+dt.timedelta(days=4)).strftime("%d %B %Y")
+    banner = "This service will be at risk from "+start_date+" to "+end_date+" due to COSMA <a href='/flamingo/support/at_risk.html'>scheduled down time</a>"
+else:
+    banner = None
+
+html_theme_options = {
+    "banner_text": banner,
+}
+
 # Immaterial
 #extensions = ["sphinx_immaterial"]
 #html_theme = 'sphinx_immaterial'
diff --git a/source/support/at_risk.rst b/source/support/at_risk.rst
new file mode 100644
index 0000000..9b586d1
--- /dev/null
+++ b/source/support/at_risk.rst
@@ -0,0 +1,12 @@
+Scheduled down time
+===================
+
+This service is hosted at the `DiRAC <https://dirac.ac.uk/>`__ Memory
+Intensive HPC facility in Durham, UK. This facility has regular
+scheduled down time in the first full week of February, June and
+October each year.
+
+We do not expect the FLAMINGO data access service to be unavailable
+for the full duration of these periods, but there may be some down
+time and it is likely that the service will at least be restarted,
+which would interrupt any ongoing downloads.
diff --git a/source/support/index.rst b/source/support/index.rst
index f77465d..379a951 100644
--- a/source/support/index.rst
+++ b/source/support/index.rst
@@ -11,6 +11,7 @@ The following pages contain resources that might be useful to solve issues
 
    Frequently asked questions <support_faq>
    List of known issues <support_issues>
+   Scheduled down time <at_risk>
 
 If these do not resolve your problem, you can contact us in one of two ways.