diff --git a/js/common/SOMQueryParameters.js b/js/common/SOMQueryParameters.js
index 8c0b9584..ceb48056 100644
--- a/js/common/SOMQueryParameters.js
+++ b/js/common/SOMQueryParameters.js
@@ -13,6 +13,9 @@ define( function( require ) {
 
   var SOMQueryParameters = QueryStringMachine.getAll( {
 
+    // Default to displaying degrees Celsius instead of Kelvin, requested by user(s), see
+    // https://github.com/phetsims/states-of-matter/issues/216
+    defaultCelsius: { type: 'flag' }
   } );
 
   statesOfMatter.register( 'SOMQueryParameters', SOMQueryParameters );
diff --git a/js/common/view/CompositeThermometerNode.js b/js/common/view/CompositeThermometerNode.js
index 6c18eff6..0c4941ac 100644
--- a/js/common/view/CompositeThermometerNode.js
+++ b/js/common/view/CompositeThermometerNode.js
@@ -17,6 +17,7 @@ define( function( require ) {
   var Panel = require( 'SUN/Panel' );
   var PhetFont = require( 'SCENERY_PHET/PhetFont' );
   var Property = require( 'AXON/Property' );
+  var SOMQueryParameters = require( 'STATES_OF_MATTER/common/SOMQueryParameters' );
   var statesOfMatter = require( 'STATES_OF_MATTER/statesOfMatter' );
   var Text = require( 'SCENERY/nodes/Text' );
   var ThermometerNode = require( 'SCENERY_PHET/ThermometerNode' );
@@ -77,7 +78,7 @@ define( function( require ) {
     } );
 
     // @private
-    this.temperatureProperty = new Property( 'kelvin' );
+    this.temperatureProperty = new Property( SOMQueryParameters.defaultCelsius ? 'celsius' : 'kelvin' );
     var temperatureComboBox = new ComboBox(
       [
         ComboBox.createItem( this.temperatureKelvinText, 'kelvin' ),