diff --git a/internal/generatedtext/daily.go b/internal/generatedtext/daily.go
index 9cdcc24..f1323e4 100644
--- a/internal/generatedtext/daily.go
+++ b/internal/generatedtext/daily.go
@@ -1,10 +1,5 @@
 package generatedtext
 
-import (
-	"fmt"
-	"strings"
-)
-
 type Daily struct {
 	Summary             string   `json:"summary"`
 	ForecastDiscussion  []string `json:"forecast_discussion"`
@@ -13,25 +8,21 @@ type Daily struct {
 }
 
 func ValidateDaily(data []byte) (Daily, []byte, error) {
-	value, err := decodeGeneratedText[Daily](data, "daily")
-	if err != nil {
-		return Daily{}, nil, err
-	}
-
-	value.Summary = strings.TrimSpace(value.Summary)
-	value.PrecipitationTiming = strings.TrimSpace(value.PrecipitationTiming)
-	value.Confidence = strings.TrimSpace(value.Confidence)
-	value.ForecastDiscussion = trimNonEmpty(value.ForecastDiscussion)
-	if value.Summary == "" {
-		return Daily{}, nil, fmt.Errorf("daily generated text summary is required")
-	}
-	if len(value.ForecastDiscussion) == 0 {
-		return Daily{}, nil, fmt.Errorf("daily generated text forecast discussion is required")
-	}
-
-	normalized, err := normalizeGeneratedText(value, "daily")
-	if err != nil {
-		return Daily{}, nil, err
-	}
-	return value, normalized, nil
+	return validateDayStyleGeneratedText[Daily, *Daily](data, "daily")
+}
+
+func (d *Daily) dayStyleFields() dayStyleFields {
+	return dayStyleFields{
+		Summary:             d.Summary,
+		ForecastDiscussion:  d.ForecastDiscussion,
+		PrecipitationTiming: d.PrecipitationTiming,
+		Confidence:          d.Confidence,
+	}
+}
+
+func (d *Daily) setDayStyleFields(fields dayStyleFields) {
+	d.Summary = fields.Summary
+	d.ForecastDiscussion = fields.ForecastDiscussion
+	d.PrecipitationTiming = fields.PrecipitationTiming
+	d.Confidence = fields.Confidence
 }
diff --git a/internal/generatedtext/day_style.go b/internal/generatedtext/day_style.go
new file mode 100644
index 0000000..48076e6
--- /dev/null
+++ b/internal/generatedtext/day_style.go
@@ -0,0 +1,63 @@
+package generatedtext
+
+import (
+	"fmt"
+	"strings"
+)
+
+type dayStyleFields struct {
+	Summary             string
+	ForecastDiscussion  []string
+	PrecipitationTiming string
+	Confidence          string
+}
+
+type dayStyleGeneratedText interface {
+	dayStyleFields() dayStyleFields
+	setDayStyleFields(dayStyleFields)
+}
+
+func validateDayStyleGeneratedText[T any, PT interface {
+	*T
+	dayStyleGeneratedText
+}](data []byte, name string) (T, []byte, error) {
+	value, err := decodeGeneratedText[T](data, name)
+	if err != nil {
+		var zero T
+		return zero, nil, err
+	}
+
+	pointer := PT(&value)
+	fields := pointer.dayStyleFields()
+	fields.Summary = strings.TrimSpace(fields.Summary)
+	fields.PrecipitationTiming = strings.TrimSpace(fields.PrecipitationTiming)
+	fields.Confidence = strings.TrimSpace(fields.Confidence)
+	fields.ForecastDiscussion = trimNonEmpty(fields.ForecastDiscussion)
+	if fields.Summary == "" {
+		var zero T
+		return zero, nil, fmt.Errorf("%s generated text summary is required", name)
+	}
+	if len(fields.ForecastDiscussion) == 0 {
+		var zero T
+		return zero, nil, fmt.Errorf("%s generated text forecast discussion is required", name)
+	}
+	pointer.setDayStyleFields(fields)
+
+	normalized, err := normalizeGeneratedText(value, name)
+	if err != nil {
+		var zero T
+		return zero, nil, err
+	}
+	return value, normalized, nil
+}
+
+func trimNonEmpty(values []string) []string {
+	out := make([]string, 0, len(values))
+	for _, value := range values {
+		trimmed := strings.TrimSpace(value)
+		if trimmed != "" {
+			out = append(out, trimmed)
+		}
+	}
+	return out
+}
diff --git a/internal/generatedtext/day_style_test.go b/internal/generatedtext/day_style_test.go
new file mode 100644
index 0000000..b337594
--- /dev/null
+++ b/internal/generatedtext/day_style_test.go
@@ -0,0 +1,131 @@
+package generatedtext
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func TestValidateDayStyleGeneratedTextSharedBehavior(t *testing.T) {
+	reports := []struct {
+		name     string
+		validate func([]byte) (any, []byte, error)
+	}{
+		{
+			name: "daily",
+			validate: func(data []byte) (any, []byte, error) {
+				value, normalized, err := ValidateDaily(data)
+				return value, normalized, err
+			},
+		},
+		{
+			name: "today",
+			validate: func(data []byte) (any, []byte, error) {
+				value, normalized, err := ValidateToday(data)
+				return value, normalized, err
+			},
+		},
+		{
+			name: "tomorrow",
+			validate: func(data []byte) (any, []byte, error) {
+				value, normalized, err := ValidateTomorrow(data)
+				return value, normalized, err
+			},
+		},
+	}
+
+	for _, report := range reports {
+		t.Run(report.name, func(t *testing.T) {
+			t.Run("requires summary", func(t *testing.T) {
+				_, _, err := report.validate([]byte(`{"forecast_discussion":["First paragraph."]}`))
+				want := fmt.Sprintf("%s generated text summary is required", report.name)
+				if err == nil || err.Error() != want {
+					t.Fatalf("validate() error = %v, want %q", err, want)
+				}
+			})
+
+			t.Run("requires non-empty forecast discussion", func(t *testing.T) {
+				_, _, err := report.validate([]byte(`{"summary":"Shared summary.","forecast_discussion":["  ",""]}`))
+				want := fmt.Sprintf("%s generated text forecast discussion is required", report.name)
+				if err == nil || err.Error() != want {
+					t.Fatalf("validate() error = %v, want %q", err, want)
+				}
+			})
+
+			t.Run("trims and normalizes", func(t *testing.T) {
+				value, normalized, err := report.validate([]byte(`{
+					"summary": " Shared summary. ",
+					"forecast_discussion": [
+						" First paragraph. ",
+						"",
+						" Second paragraph. "
+					],
+					"precipitation_timing": " Afternoon. ",
+					"confidence": " Medium "
+				}`))
+				if err != nil {
+					t.Fatalf("validate() error = %v", err)
+				}
+				fields := dayStyleFieldsForTest(t, value)
+				if fields.Summary != "Shared summary." {
+					t.Fatalf("Summary = %q, want trimmed summary", fields.Summary)
+				}
+				if strings.Join(fields.ForecastDiscussion, "|") != "First paragraph.|Second paragraph." {
+					t.Fatalf("ForecastDiscussion = %#v, want trimmed non-empty paragraphs", fields.ForecastDiscussion)
+				}
+				if fields.PrecipitationTiming != "Afternoon." {
+					t.Fatalf("PrecipitationTiming = %q, want trimmed precipitation timing", fields.PrecipitationTiming)
+				}
+				if fields.Confidence != "Medium" {
+					t.Fatalf("Confidence = %q, want trimmed confidence", fields.Confidence)
+				}
+				want := `{"summary":"Shared summary.","forecast_discussion":["First paragraph.","Second paragraph."],"precipitation_timing":"Afternoon.","confidence":"Medium"}`
+				if string(normalized) != want {
+					t.Fatalf("normalized = %s, want %s", normalized, want)
+				}
+			})
+
+			t.Run("omits empty optional fields", func(t *testing.T) {
+				_, normalized, err := report.validate([]byte(`{
+					"summary": "Shared summary.",
+					"forecast_discussion": ["First paragraph."],
+					"precipitation_timing": "   ",
+					"confidence": "   "
+				}`))
+				if err != nil {
+					t.Fatalf("validate() error = %v", err)
+				}
+				want := `{"summary":"Shared summary.","forecast_discussion":["First paragraph."]}`
+				if string(normalized) != want {
+					t.Fatalf("normalized = %s, want %s", normalized, want)
+				}
+			})
+
+			t.Run("rejects unknown fields", func(t *testing.T) {
+				_, _, err := report.validate([]byte(`{"summary":"Shared summary.","forecast_discussion":["First paragraph."],"extra":"value"}`))
+				if err == nil {
+					t.Fatal("validate() error = nil, want error")
+				}
+				if !strings.Contains(err.Error(), `unknown field "extra"`) {
+					t.Fatalf("validate() error = %v, want unknown field error", err)
+				}
+			})
+		})
+	}
+}
+
+func dayStyleFieldsForTest(t *testing.T, value any) dayStyleFields {
+	t.Helper()
+
+	switch value := value.(type) {
+	case Daily:
+		return (&value).dayStyleFields()
+	case Today:
+		return (&value).dayStyleFields()
+	case Tomorrow:
+		return (&value).dayStyleFields()
+	default:
+		t.Fatalf("value type = %T, want day-style generated text", value)
+		return dayStyleFields{}
+	}
+}
diff --git a/internal/generatedtext/today.go b/internal/generatedtext/today.go
index 5137dda..b400fa7 100644
--- a/internal/generatedtext/today.go
+++ b/internal/generatedtext/today.go
@@ -1,10 +1,5 @@
 package generatedtext
 
-import (
-	"fmt"
-	"strings"
-)
-
 type Today struct {
 	Summary             string   `json:"summary"`
 	ForecastDiscussion  []string `json:"forecast_discussion"`
@@ -13,25 +8,21 @@ type Today struct {
 }
 
 func ValidateToday(data []byte) (Today, []byte, error) {
-	value, err := decodeGeneratedText[Today](data, "today")
-	if err != nil {
-		return Today{}, nil, err
-	}
-
-	value.Summary = strings.TrimSpace(value.Summary)
-	value.PrecipitationTiming = strings.TrimSpace(value.PrecipitationTiming)
-	value.Confidence = strings.TrimSpace(value.Confidence)
-	value.ForecastDiscussion = trimNonEmpty(value.ForecastDiscussion)
-	if value.Summary == "" {
-		return Today{}, nil, fmt.Errorf("today generated text summary is required")
-	}
-	if len(value.ForecastDiscussion) == 0 {
-		return Today{}, nil, fmt.Errorf("today generated text forecast discussion is required")
-	}
-
-	normalized, err := normalizeGeneratedText(value, "today")
-	if err != nil {
-		return Today{}, nil, err
-	}
-	return value, normalized, nil
+	return validateDayStyleGeneratedText[Today, *Today](data, "today")
+}
+
+func (t *Today) dayStyleFields() dayStyleFields {
+	return dayStyleFields{
+		Summary:             t.Summary,
+		ForecastDiscussion:  t.ForecastDiscussion,
+		PrecipitationTiming: t.PrecipitationTiming,
+		Confidence:          t.Confidence,
+	}
+}
+
+func (t *Today) setDayStyleFields(fields dayStyleFields) {
+	t.Summary = fields.Summary
+	t.ForecastDiscussion = fields.ForecastDiscussion
+	t.PrecipitationTiming = fields.PrecipitationTiming
+	t.Confidence = fields.Confidence
 }
diff --git a/internal/generatedtext/tomorrow.go b/internal/generatedtext/tomorrow.go
index f9590c7..8854acc 100644
--- a/internal/generatedtext/tomorrow.go
+++ b/internal/generatedtext/tomorrow.go
@@ -1,10 +1,5 @@
 package generatedtext
 
-import (
-	"fmt"
-	"strings"
-)
-
 type Tomorrow struct {
 	Summary             string   `json:"summary"`
 	ForecastDiscussion  []string `json:"forecast_discussion"`
@@ -13,36 +8,21 @@ type Tomorrow struct {
 }
 
 func ValidateTomorrow(data []byte) (Tomorrow, []byte, error) {
-	value, err := decodeGeneratedText[Tomorrow](data, "tomorrow")
-	if err != nil {
-		return Tomorrow{}, nil, err
-	}
-
-	value.Summary = strings.TrimSpace(value.Summary)
-	value.PrecipitationTiming = strings.TrimSpace(value.PrecipitationTiming)
-	value.Confidence = strings.TrimSpace(value.Confidence)
-	value.ForecastDiscussion = trimNonEmpty(value.ForecastDiscussion)
-	if value.Summary == "" {
-		return Tomorrow{}, nil, fmt.Errorf("tomorrow generated text summary is required")
-	}
-	if len(value.ForecastDiscussion) == 0 {
-		return Tomorrow{}, nil, fmt.Errorf("tomorrow generated text forecast discussion is required")
-	}
-
-	normalized, err := normalizeGeneratedText(value, "tomorrow")
-	if err != nil {
-		return Tomorrow{}, nil, err
-	}
-	return value, normalized, nil
+	return validateDayStyleGeneratedText[Tomorrow, *Tomorrow](data, "tomorrow")
 }
 
-func trimNonEmpty(values []string) []string {
-	out := make([]string, 0, len(values))
-	for _, value := range values {
-		trimmed := strings.TrimSpace(value)
-		if trimmed != "" {
-			out = append(out, trimmed)
-		}
+func (t *Tomorrow) dayStyleFields() dayStyleFields {
+	return dayStyleFields{
+		Summary:             t.Summary,
+		ForecastDiscussion:  t.ForecastDiscussion,
+		PrecipitationTiming: t.PrecipitationTiming,
+		Confidence:          t.Confidence,
 	}
-	return out
+}
+
+func (t *Tomorrow) setDayStyleFields(fields dayStyleFields) {
+	t.Summary = fields.Summary
+	t.ForecastDiscussion = fields.ForecastDiscussion
+	t.PrecipitationTiming = fields.PrecipitationTiming
+	t.Confidence = fields.Confidence
 }