diff --git a/airflow/sensors/base_sensor_operator.py b/airflow/sensors/base_sensor_operator.py
index 5e7910b621175c..9d421932c8675e 100644
--- a/airflow/sensors/base_sensor_operator.py
+++ b/airflow/sensors/base_sensor_operator.py
@@ -20,6 +20,7 @@
 
 from time import sleep
 from datetime import timedelta
+from typing import Dict, Iterable
 
 from airflow.exceptions import AirflowException, AirflowSensorTimeout, \
     AirflowSkipException, AirflowRescheduleException
@@ -57,17 +58,17 @@ class BaseSensorOperator(BaseOperator, SkipMixin):
         prevent too much load on the scheduler.
     :type mode: str
     """
-    ui_color = '#e6f1f2'
-    valid_modes = ['poke', 'reschedule']
+    ui_color = '#e6f1f2'  # type: str
+    valid_modes = ['poke', 'reschedule']  # type: Iterable[str]
 
     @apply_defaults
     def __init__(self,
-                 poke_interval=60,
-                 timeout=60 * 60 * 24 * 7,
-                 soft_fail=False,
-                 mode='poke',
+                 poke_interval: float = 60,
+                 timeout: float = 60 * 60 * 24 * 7,
+                 soft_fail: bool = False,
+                 mode: str = 'poke',
                  *args,
-                 **kwargs):
+                 **kwargs) -> None:
         super().__init__(*args, **kwargs)
         self.poke_interval = poke_interval
         self.soft_fail = soft_fail
@@ -75,7 +76,7 @@ def __init__(self,
         self.mode = mode
         self._validate_input_values()
 
-    def _validate_input_values(self):
+    def _validate_input_values(self) -> None:
         if not isinstance(self.poke_interval, (int, float)) or self.poke_interval < 0:
             raise AirflowException(
                 "The poke_interval must be a non-negative number")
@@ -90,14 +91,14 @@ def _validate_input_values(self):
                         d=self.dag.dag_id if self.dag else "",
                         t=self.task_id, m=self.mode))
 
-    def poke(self, context):
+    def poke(self, context: Dict) -> bool:
         """
         Function that the sensors defined while deriving this class should
         override.
         """
         raise AirflowException('Override me.')
 
-    def execute(self, context):
+    def execute(self, context: Dict) -> None:
         started_at = timezone.utcnow()
         if self.reschedule:
             # If reschedule, use first start date of current try
@@ -122,7 +123,7 @@ def execute(self, context):
                 sleep(self.poke_interval)
         self.log.info("Success criteria met. Exiting.")
 
-    def _do_skip_downstream_tasks(self, context):
+    def _do_skip_downstream_tasks(self, context: Dict) -> None:
         downstream_tasks = context['task'].get_flat_relatives(upstream=False)
         self.log.debug("Downstream task_ids %s", downstream_tasks)
         if downstream_tasks: