diff --git a/lib/microwaveprop/workers/propagation_grid_worker.ex b/lib/microwaveprop/workers/propagation_grid_worker.ex
index 759c1424..4ce7cd7d 100644
--- a/lib/microwaveprop/workers/propagation_grid_worker.ex
+++ b/lib/microwaveprop/workers/propagation_grid_worker.ex
@@ -21,7 +21,7 @@ defmodule Microwaveprop.Workers.PropagationGridWorker do
   def perform(%Oban.Job{}) do
     # HRRR takes ~45min to publish after the hour. Use 2 hours ago to ensure availability.
     two_hours_ago = DateTime.add(DateTime.utc_now(), -2, :hour)
-    valid_time = HrrrClient.nearest_hrrr_hour(two_hours_ago)
+    valid_time = two_hours_ago |> HrrrClient.nearest_hrrr_hour() |> DateTime.truncate(:second)
     points = Grid.conus_points()
 
     Logger.info("PropagationGrid: pausing backfill queues, fetching HRRR for #{valid_time}, #{length(points)} points")