diff --git a/internal/adapters/httpapi/server_test.go b/internal/adapters/httpapi/server_test.go
index 1d6300e..9fa80ee 100644
--- a/internal/adapters/httpapi/server_test.go
+++ b/internal/adapters/httpapi/server_test.go
@@ -232,3 +232,70 @@ func TestForecastReturnsUSUnits(t *testing.T) {
 		t.Fatalf("expected forecast timestamp passed to repo")
 	}
 }
+
+func TestNullFieldsAreOmittedFromJSON(t *testing.T) {
+	obsRepo := &fakeObservationRepo{
+		summary: ports.ObservationSummaryMetric{},
+		conditions: []ports.ObservationConditionMetric{
+			{
+				ObservedAt: time.Date(2026, 3, 17, 12, 0, 0, 0, time.UTC),
+			},
+		},
+	}
+	fcRepo := &fakeForecastRepo{
+		periods: []ports.ForecastPeriodMetric{
+			{
+				PeriodIndex:   1,
+				StartTime:     time.Date(2026, 3, 17, 12, 0, 0, 0, time.UTC),
+				EndTime:       time.Date(2026, 3, 17, 13, 0, 0, 0, time.UTC),
+				ConditionCode: 1,
+			},
+		},
+	}
+
+	server := NewServer(
+		observations.NewService(obsRepo, units.USConverter{}, constants.ObservationWindow),
+		forecasts.NewService(fcRepo, units.USConverter{}, constants.ForecastQueryLimit),
+		alerts.NewService(fakeAlertRepo{}),
+	).Handler()
+
+	wObs := httptest.NewRecorder()
+	server.ServeHTTP(wObs, httptest.NewRequest(http.MethodGet, "/observations/current", nil))
+	if wObs.Code != http.StatusOK {
+		t.Fatalf("expected observations 200, got %d", wObs.Code)
+	}
+
+	var obsPayload map[string]any
+	if err := json.Unmarshal(wObs.Body.Bytes(), &obsPayload); err != nil {
+		t.Fatalf("decode observations response: %v", err)
+	}
+	summary := obsPayload["summary"].(map[string]any)
+	if _, exists := summary["temperatureF"]; exists {
+		t.Fatalf("expected summary.temperatureF to be omitted when nil")
+	}
+
+	conditions := obsPayload["conditions"].([]any)
+	firstCond := conditions[0].(map[string]any)
+	if _, exists := firstCond["temperatureF"]; exists {
+		t.Fatalf("expected conditions[0].temperatureF to be omitted when nil")
+	}
+
+	wFc := httptest.NewRecorder()
+	server.ServeHTTP(wFc, httptest.NewRequest(http.MethodGet, "/forecast?timestamp=2026-03-17T12:30:00Z", nil))
+	if wFc.Code != http.StatusOK {
+		t.Fatalf("expected forecast 200, got %d", wFc.Code)
+	}
+
+	var fcPayload map[string]any
+	if err := json.Unmarshal(wFc.Body.Bytes(), &fcPayload); err != nil {
+		t.Fatalf("decode forecast response: %v", err)
+	}
+	periods := fcPayload["periods"].([]any)
+	firstPeriod := periods[0].(map[string]any)
+	if _, exists := firstPeriod["temperatureF"]; exists {
+		t.Fatalf("expected periods[0].temperatureF to be omitted when nil")
+	}
+	if _, exists := firstPeriod["windSpeedMph"]; exists {
+		t.Fatalf("expected periods[0].windSpeedMph to be omitted when nil")
+	}
+}
diff --git a/internal/application/alerts/service.go b/internal/application/alerts/service.go
index e9a9fea..094407f 100644
--- a/internal/application/alerts/service.go
+++ b/internal/application/alerts/service.go
@@ -21,13 +21,13 @@ type Response struct {
 }
 
 type AlertResponse struct {
-	Effective   *time.Time `json:"effective"`
-	Expires     *time.Time `json:"expires"`
-	Severity    *string    `json:"severity"`
-	Event       *string    `json:"event"`
-	Headline    *string    `json:"headline"`
-	Instruction *string    `json:"instruction"`
-	Description *string    `json:"description"`
+	Effective   *time.Time `json:"effective,omitempty"`
+	Expires     *time.Time `json:"expires,omitempty"`
+	Severity    *string    `json:"severity,omitempty"`
+	Event       *string    `json:"event,omitempty"`
+	Headline    *string    `json:"headline,omitempty"`
+	Instruction *string    `json:"instruction,omitempty"`
+	Description *string    `json:"description,omitempty"`
 }
 
 func (s *Service) GetCurrent(ctx context.Context) (Response, error) {
diff --git a/internal/application/forecasts/service.go b/internal/application/forecasts/service.go
index a9c82ba..12c9267 100644
--- a/internal/application/forecasts/service.go
+++ b/internal/application/forecasts/service.go
@@ -28,30 +28,30 @@ type PeriodResponse struct {
 	PeriodIndex                       int       `json:"periodIndex"`
 	StartTime                         time.Time `json:"startTime"`
 	EndTime                           time.Time `json:"endTime"`
-	Name                              *string   `json:"name"`
-	IsDay                             *bool     `json:"isDay"`
+	Name                              *string   `json:"name,omitempty"`
+	IsDay                             *bool     `json:"isDay,omitempty"`
 	ConditionCode                     int       `json:"conditionCode"`
-	ConditionText                     *string   `json:"conditionText"`
-	ProviderRawDescription            *string   `json:"providerRawDescription"`
-	TextDescription                   *string   `json:"textDescription"`
-	DetailedText                      *string   `json:"detailedText"`
-	IconURL                           *string   `json:"iconUrl"`
-	TemperatureF                      *float64  `json:"temperatureF"`
-	TemperatureFMin                   *float64  `json:"temperatureFMin"`
-	TemperatureFMax                   *float64  `json:"temperatureFMax"`
-	DewpointF                         *float64  `json:"dewpointF"`
-	RelativeHumidityPercent           *float64  `json:"relativeHumidityPercent"`
-	WindDirectionDegrees              *float64  `json:"windDirectionDegrees"`
-	WindSpeedMph                      *float64  `json:"windSpeedMph"`
-	WindGustMph                       *float64  `json:"windGustMph"`
-	BarometricPressurePa              *float64  `json:"barometricPressurePa"`
-	VisibilityMeters                  *float64  `json:"visibilityMeters"`
-	ApparentTemperatureF              *float64  `json:"apparentTemperatureF"`
-	CloudCoverPercent                 *float64  `json:"cloudCoverPercent"`
-	ProbabilityOfPrecipitationPercent *float64  `json:"probabilityOfPrecipitationPercent"`
-	PrecipitationAmountMm             *float64  `json:"precipitationAmountMm"`
-	SnowfallDepthMm                   *float64  `json:"snowfallDepthMm"`
-	UVIndex                           *float64  `json:"uvIndex"`
+	ConditionText                     *string   `json:"conditionText,omitempty"`
+	ProviderRawDescription            *string   `json:"providerRawDescription,omitempty"`
+	TextDescription                   *string   `json:"textDescription,omitempty"`
+	DetailedText                      *string   `json:"detailedText,omitempty"`
+	IconURL                           *string   `json:"iconUrl,omitempty"`
+	TemperatureF                      *float64  `json:"temperatureF,omitempty"`
+	TemperatureFMin                   *float64  `json:"temperatureFMin,omitempty"`
+	TemperatureFMax                   *float64  `json:"temperatureFMax,omitempty"`
+	DewpointF                         *float64  `json:"dewpointF,omitempty"`
+	RelativeHumidityPercent           *float64  `json:"relativeHumidityPercent,omitempty"`
+	WindDirectionDegrees              *float64  `json:"windDirectionDegrees,omitempty"`
+	WindSpeedMph                      *float64  `json:"windSpeedMph,omitempty"`
+	WindGustMph                       *float64  `json:"windGustMph,omitempty"`
+	BarometricPressurePa              *float64  `json:"barometricPressurePa,omitempty"`
+	VisibilityMeters                  *float64  `json:"visibilityMeters,omitempty"`
+	ApparentTemperatureF              *float64  `json:"apparentTemperatureF,omitempty"`
+	CloudCoverPercent                 *float64  `json:"cloudCoverPercent,omitempty"`
+	ProbabilityOfPrecipitationPercent *float64  `json:"probabilityOfPrecipitationPercent,omitempty"`
+	PrecipitationAmountMm             *float64  `json:"precipitationAmountMm,omitempty"`
+	SnowfallDepthMm                   *float64  `json:"snowfallDepthMm,omitempty"`
+	UVIndex                           *float64  `json:"uvIndex,omitempty"`
 }
 
 func (s *Service) GetByTimestamp(ctx context.Context, ts time.Time) (Response, error) {
diff --git a/internal/application/observations/service.go b/internal/application/observations/service.go
index 85a04b0..2c9633d 100644
--- a/internal/application/observations/service.go
+++ b/internal/application/observations/service.go
@@ -26,18 +26,18 @@ type CurrentResponse struct {
 }
 
 type SummaryResponse struct {
-	TemperatureF         *float64 `json:"temperatureF"`
-	ApparentTemperatureF *float64 `json:"apparentTemperatureF"`
+	TemperatureF         *float64 `json:"temperatureF,omitempty"`
+	ApparentTemperatureF *float64 `json:"apparentTemperatureF,omitempty"`
 	WindowMinutes        int      `json:"windowMinutes"`
 }
 
 type ConditionResponse struct {
-	StationID              *string   `json:"stationId"`
+	StationID              *string   `json:"stationId,omitempty"`
 	ObservedAt             time.Time `json:"observedAt"`
-	TemperatureF           *float64  `json:"temperatureF"`
-	TextDescription        *string   `json:"textDescription"`
-	ProviderRawDescription *string   `json:"providerRawDescription"`
-	ConditionText          *string   `json:"conditionText"`
+	TemperatureF           *float64  `json:"temperatureF,omitempty"`
+	TextDescription        *string   `json:"textDescription,omitempty"`
+	ProviderRawDescription *string   `json:"providerRawDescription,omitempty"`
+	ConditionText          *string   `json:"conditionText,omitempty"`
 }
 
 func (s *Service) GetCurrent(ctx context.Context) (CurrentResponse, error) {