diff --git a/Source/Diagnostics/FullDiagnostics.H b/Source/Diagnostics/FullDiagnostics.H
index 1b999a9b361..a58c2485c8f 100644
--- a/Source/Diagnostics/FullDiagnostics.H
+++ b/Source/Diagnostics/FullDiagnostics.H
@@ -4,6 +4,8 @@
 #include "Diagnostics.H"
 #include "Utils/Parser/IntervalsParser.H"
 
+#include <AMReX_REAL.H>
+
 #include <string>
 
 class FullDiagnostics final : public Diagnostics
@@ -25,6 +27,12 @@ private:
      * before writing the diagnostic.
      */
     bool m_solver_deposits_current = true;
+    /** Whether the diagnostics are averaging data over time or not */
+    bool m_do_time_averaging = false;
+    /** Period to average fields over: in steps */
+    unsigned int m_average_period_steps = 0;
+    /** Period to average fields over: in seconds */
+    amrex::Real m_average_period_seconds = 0;
     /** Flush m_mf_output and particles to file for the i^th buffer */
     void Flush (int i_buffer, bool /* force_flush */) override;
     /** Flush raw data */
diff --git a/Source/Diagnostics/MultiDiagnostics.H b/Source/Diagnostics/MultiDiagnostics.H
index d220396ed12..75b51527242 100644
--- a/Source/Diagnostics/MultiDiagnostics.H
+++ b/Source/Diagnostics/MultiDiagnostics.H
@@ -12,7 +12,7 @@
 #include <vector>
 
 /** All types of diagnostics. */
-enum struct DiagTypes {Full, BackTransformed, BoundaryScraping};
+enum struct DiagTypes {Full, BackTransformed, BoundaryScraping, TimeAveraged};
 
 /**
  * \brief This class contains a vector of all diagnostics in the simulation.