For **segment triggered flows**, if you want your flow to send as soon as data refreshes you can choose **send immediately when segment updates** when [creating your flow](🔗).
However, if you want to avoid sending during certain hours, e.g. during the night, you can specify a specific window during which flows will send. You actually accomplish this by specifying the only time you _do_ want messages to send. During this _send window_, any time the data refreshes, your flow will send again during that time period.
For example, if you set a send window to 3-9 PM, any time the flow data refreshes within those 6 hours, your triggered message will send. However, even if the data refreshes at 9:30 PM, the message won't send again until that send window opens up at 3 PM the next day, and only if the receiver is still a member of the segment.
## Data pipes, loads, and send times
This diagram illustrates how data pipes and loads affect send time within a set send window.
6 hour increments
Send windows must be six hours at minimum. For windows less than six hours, use a [**send time**](🔗), which has a two hour send window on its own.
# How to set a send window
Segment triggered flows
Send windows are only available for segment triggered flows
Create a triggered [flow](🔗).
Configure the trigger to _When a contact enters the segment_.
Choose your segment and configure options, then scroll down to the next section, **Send Time**.
Under **Send Time**:
Choose **Send immediately when segment updates.**
Check **Only send at certain times**.
From the drop downs, choose a **Timezone** the window will be based on, then the associated **Hours** and **Minutes** that include your send window. The window must be at least six hours long.
Complete your [flow](🔗) as usual.