diff --git a/cmd/ingestd/main.go b/cmd/ingestd/main.go
index 464f569..8f61d20 100644
--- a/cmd/ingestd/main.go
+++ b/cmd/ingestd/main.go
@@ -46,6 +46,9 @@ func main() {
 			log.Fatalf("site timezone load: %v", err)
 		}
 		rainDayLoc = loc
+		log.Printf("site timezone configured: %s", cfg.Site.Timezone)
+	} else {
+		log.Printf("site timezone not set; falling back to process local timezone: %s", time.Local)
 	}
 	log.Printf("rain day timezone: %s", rainDayLoc)
 
diff --git a/internal/config/config.go b/internal/config/config.go
index 2dd8771..1e13707 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -107,6 +107,9 @@ func Load(path string) (*Config, error) {
 	if c.Site.Name == "" {
 		c.Site.Name = "default"
 	}
+	if c.Wunderground.Enabled && c.Site.Timezone == "" {
+		return nil, errors.New("site timezone is required when wunderground is enabled (used for daily rain boundary)")
+	}
 	if c.Site.Timezone != "" {
 		if _, err := time.LoadLocation(c.Site.Timezone); err != nil {
 			return nil, fmt.Errorf("invalid site timezone %q: %w", c.Site.Timezone, err)