diff --git a/rivretrieve/constants.py b/rivretrieve/constants.py
index 7d05a05..e403c1a 100644
--- a/rivretrieve/constants.py
+++ b/rivretrieve/constants.py
@@ -24,6 +24,7 @@
 DAILY = "daily"
 HOURLY = "hourly"
 INSTANTANEOUS = "instantaneous"
+MONTHLY = "monthly"
 
 # List of temporal aggregrations.
 _MEAN = "mean"
@@ -39,6 +40,9 @@
 DISCHARGE_DAILY_MIN = f"{DISCHARGE}_{DAILY}_{_MIN}"
 DISCHARGE_HOURLY_MEAN = f"{DISCHARGE}_{HOURLY}_{_MEAN}"
 DISCHARGE_INSTANT = f"{DISCHARGE}_{INSTANTANEOUS}"
+DISCHARGE_MONTHLY_MEAN = f"{DISCHARGE}_{MONTHLY}_{_MEAN}"
+DISCHARGE_MONTHLY_MAX = f"{DISCHARGE}_{MONTHLY}_{_MIN}"
+DISCHARGE_MONTHLY_MIN = f"{DISCHARGE}_{MONTHLY}_{_MAX}"
 
 # Stage.
 STAGE_DAILY_MEAN = f"{STAGE}_{DAILY}_{_MEAN}"
@@ -46,11 +50,17 @@
 STAGE_DAILY_MIN = f"{STAGE}_{DAILY}_{_MIN}"
 STAGE_HOURLY_MEAN = f"{STAGE}_{HOURLY}_{_MEAN}"
 STAGE_INSTANT = f"{STAGE}_{INSTANTANEOUS}"
+STAGE_MONTHLY_MEAN = f"{STAGE}_{MONTHLY}_{_MEAN}"
+STAGE_MONTHLY_MAX = f"{STAGE}_{MONTHLY}_{_MIN}"
+STAGE_MONTHLY_MIN = f"{STAGE}_{MONTHLY}_{_MAX}"
 
 # Water temperature.
 WATER_TEMPERATURE_DAILY_MEAN = f"{_WATER_TEMPERATURE}_{DAILY}_{_MEAN}"
+WATER_TEMPERATURE_DAILY_MAX = f"{_WATER_TEMPERATURE}_{DAILY}_{_MAX}"
+WATER_TEMPERATURE_DAILY_MIN = f"{_WATER_TEMPERATURE}_{DAILY}_{_MIN}"
 WATER_TEMPERATURE_HOURLY_MEAN = f"{_WATER_TEMPERATURE}_{HOURLY}_{_MEAN}"
 WATER_TEMPERATURE_INSTANT = f"{_WATER_TEMPERATURE}_{INSTANTANEOUS}"
+WATER_TEMPERATURE_MONTHLY_MEAN = f"{_WATER_TEMPERATURE}_{MONTHLY}_{_MEAN}"
 
 # Precipitation
 CATCHMENT_PRECIPITATION_DAILY_SUM = f"{_CATCHMENT_PRECIPITATION}_{DAILY}_{_SUM}"