This report describes the typical weather at the Gerald R. Ford International Airport (Grand Rapids, Michigan, United States) weather station over the course of an average October. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Grand Rapids, Michigan has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by grasslands (56%), forests (27%), croplands (12%), and built-up areas (4%).
The month of October is characterized by rapidly falling daily high temperatures, with daily highs decreasing from 65°F to 54°F over the course of the month, exceeding 77°F or dropping below 42°F only one day in ten.
Over the course of October, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 1:24 hours, implying an average day-over-day decrease of 2.7 minutes.
The shortest day of the month is October 31 with 10:19 hours of daylight; the longest day is October 1 with 11:43 hours of daylight.
The earliest sunrise is at 7:40am on October 1; the latest sunset is at 7:23pm on October 1; the latest sunrise is at 8:16am on October 31; the earliest sunset is at 6:35pm on October 31.
Daylight savings time is observed in 2012 but it neither starts nor ends in October, so the entire month is in daylight time.
The median cloud cover ranges from 70% (partly cloudy) to 89% (mostly cloudy). The trend is for the sky to be becoming rapidly cloudier with the median cloud cover increasing by 19% from the start to the end of the month.
On October 1, the clearest day of the month, the sky is clear, mostly clear, or partly cloudy 51% of the time, and overcast or mostly cloudy 49% of the time.
On October 31, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 72% of the time, and clear or mostly clear 27% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around October 31, occurring in 53% of days. Precipitation is least likely around October 1, occurring in 45% of days.
Throughout October, the most common forms of precipitation are light rain, moderate rain, light snow, and thunderstorms.
Light rain is the most severe precipitation observed during 37% of those days with precipitation. It is most likely around October 17, when it is observed during 19% of all days.
Moderate rain is the most severe precipitation observed during 31% of those days with precipitation. It is most likely around October 13, when it is observed during 16% of all days.
Light snow is the most severe precipitation observed during 11% of those days with precipitation. It is most likely around October 31, when it is observed during 11% of all days.
Thunderstorms are the most severe precipitation observed during 11% of those days with precipitation. They are most likely around October 1, when it is observed during 7% of all days.
The likelihood of snow falling is highest around October 31, occurring in 15% of days.
Either snow rarely accumulates at this location in October or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 52% (mildly humid) to 93% (very humid) over the course of a typical October, rarely dropping below 37% (comfortable) and reaching as high as 100% (very humid).
The air is driest around October 3, at which time the relative humidity drops below 60% (mildly humid) three days out of four; it is most humid around October 1, rising above 90% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical October, the dew point typically varies from 31°F (dry) to 52°F (very comfortable) and is rarely below 22°F (dry) or above 63°F (mildy humid).
Over the course of October typical wind speeds vary from 2 mph to 16 mph (light air to moderate breeze), rarely exceeding 23 mph (fresh breeze).
The highest average wind speed of 10 mph (gentle breeze) occurs around October 31, at which time the average daily maximum wind speed is 16 mph (moderate breeze).
The lowest average wind speed of 9 mph (gentle breeze) occurs around October 1, at which time the average daily maximum wind speed is 15 mph (moderate breeze).