Most people think of the hour between 9 and 10 a.m. as the middle of the morning. Most people think of mid-morning as the time between sunrise and noon, which can be a little different depending on the season. The workday, on the other hand, may start at 8 a.m. no matter what time of year it is. This makes the time between 9 a.m. and 10 a.m. a fairly constant and predictable time for midmorning. Depending on how people plan their days, these mid-morning hours may also be when people are getting to work.
If you want to know what midmorning is, it can also help to look at what morning is. Merriam-Webster says that morning is “the time from sunrise to noon,” and midmorning is “the middle of the time from sunrise to noon or from the start of normal daily activities to noon.”
Because the time of sunrise changes a lot from season to season, it may be easier to think of mid-morning in terms of the second part of the definition: “from the start of the normal time of daily activities to noon.” No matter the season, many people wake up around 6 a.m. to start getting ready for work at 8 or 9 a.m. If 6 a.m. is the beginning of the morning and noon is the end, then 9 a.m. is exactly in the middle, making it a good time for mid-morning.