diff --git a/src/actions/recomputeReduxState.js b/src/actions/recomputeReduxState.js
index 931228b02..d3941a526 100644
--- a/src/actions/recomputeReduxState.js
+++ b/src/actions/recomputeReduxState.js
@@ -11,6 +11,7 @@ import { getDefaultMeasurementsState } from "../reducers/measurements";
 import { countTraitsAcrossTree, calcTotalTipsInTree } from "../util/treeCountingHelpers";
 import { calcEntropyInView } from "../util/entropy";
 import { treeJsonToState } from "../util/treeJsonProcessing";
+import { castIncorrectTypes } from "../util/castJsonTypes";
 import { entropyCreateState } from "../util/entropyCreateStateFromJsons";
 import { determineColorByGenotypeMutType, calcNodeColor } from "../util/colorHelpers";
 import { calcColorScale, createVisibleLegendValues } from "../util/colorScale";
@@ -771,11 +772,13 @@ export const createStateFromQueryOrJSONs = ({
     measurements = getDefaultMeasurementsState();
     /* new tree state(s) */
     tree = treeJsonToState(json.tree);
+    castIncorrectTypes(metadata, tree);
     tree.debug = "LEFT";
     tree.name = mainTreeName;
     metadata.mainTreeNumTips = calcTotalTipsInTree(tree.nodes);
     if (secondTreeDataset) {
       treeToo = treeJsonToState(secondTreeDataset.tree);
+      castIncorrectTypes(metadata, treeToo);
       treeToo.debug = "RIGHT";
       treeToo.name = secondTreeName;
       /* TODO: calc & display num tips in 2nd tree */
diff --git a/src/util/castJsonTypes.js b/src/util/castJsonTypes.js
new file mode 100644
index 000000000..712519c0d
--- /dev/null
+++ b/src/util/castJsonTypes.js
@@ -0,0 +1,56 @@
+/**
+ * Values in the JSON should be appropriately typed however this may not always be the case.
+ * For instance, certain values of a continuous trait may be strings, and we should cast
+ * these to numbers. See https://github.com/nextstrain/auspice/issues/1626 for more discussion
+ * of this particular case. Feel free to add more checks / casts to this function!
+ * @param {Object} metadata
+ * @param {Object} tree
+ * @returns {undefined} Any type casting is in-place
+ */
+export const castIncorrectTypes = (metadata, tree) => {
+  try {
+    const continuousKeys = new Set();
+    Object.entries(metadata.colorings || {}).forEach(([key, details]) => {
+      if (details.type==="continuous") {
+        continuousKeys.add(key);
+      }
+    });
+    tree.nodes.forEach((node) => {
+      for (const key of continuousKeys) {
+        const attr = node?.node_attrs?.[key];
+        if (!attr) continue;
+        continuousAttrValueToNumber(attr);
+      }
+    });
+  } catch (err) {
+    // type casting shouldn't be required (the JSON should be correctly typed)
+    // so any errors shouldn't prevent Auspice loading
+    console.error(err);
+  }
+};
+
+/**
+ * Cast `attr.value` to either a Number or undefined.
+ * Note that "Infinity" (string) is changed to undefined, but `Infinity` (Number)
+ * is left alone as the latter is not possible to encode in JSON.
+ * @param {Record<string, any>} attr
+ */
+export function continuousAttrValueToNumber(attr) {
+  switch (typeof attr.value) {
+    case "number":
+      break;
+    case "string":
+      const value = attr.value.trim();
+      if (value === "" || isNaN(value) || value ==="Infinity" || value ==="-Infinity") {
+        // Note: Number("")=0
+        // undefined values are handled appropriately (e.g. scatterplots, tooltips etc)
+        attr.value = undefined;
+      } else {
+        attr.value = Number(value);
+      }
+      break;
+    default:
+      // any other types (Boolean, Null ('object')) are not valid for a continuous scale
+      attr.value = undefined;
+  }
+}
diff --git a/test/jsonParsing.test.js b/test/jsonParsing.test.js
new file mode 100644
index 000000000..58e35df88
--- /dev/null
+++ b/test/jsonParsing.test.js
@@ -0,0 +1,20 @@
+import { continuousAttrValueToNumber } from "../src/util/castJsonTypes";
+
+/**
+ * function used to cast node values of continuous traits to numbers
+ */
+test("Continuous scale values are cast to Numbers or are undefined", () => {
+  const numbers = ["123", "1e5", "1", "0", "-1", 0, 1, -1];
+  const notNumbers = ["", "  ", " Infinity", "infinity", "Infinity", null, "abc", "", true, false, "true", undefined];
+  numbers.forEach((n) => {
+    const attr = {value: n};
+    continuousAttrValueToNumber(attr); // modifies in place
+    expect(typeof attr.value).toStrictEqual('number');
+    expect(Number.isFinite(attr.value)).toBe(true);
+  });
+  notNumbers.forEach((n) => {
+    const attr = {value: n};
+    continuousAttrValueToNumber(attr); // modifies in place
+    expect(attr.value).toBeUndefined();
+  });
+});