2024 Compare Climate & Weather:
Great Falls, MT vs O'Fallon, IL
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Highlights
On average, there are 202 sunny days per year in O'Fallon. Great Falls averages 188 sunny days per year. The US average is 205 sunny days.
O'Fallon, Illinois gets 43.1 inches of rain, on average, per year. Great Falls, Montana gets 14.4 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.
O'Fallon averages 11.6 inches of snow per year. Great Falls averages 58 inches of snow per year. The US average is 27.8 inches of snow per year.
Weather Highlights
O'Fallon, Illinois
Summer High: the July high is around 89.2 degrees
Winter Low: the January low is 22
Rain: averages 43.1 inches of rain a year
Snow: averages 11.6 inches of snow a year
Great Falls, Montana
Summer High: the July high is around 85.3 degrees
Winter Low: the January low is 16.6
Rain: averages 14.4 inches of rain a year
Snow: averages 58 inches of snow a year
BESTPLACES COMFORT INDEX
O'FallonThe annual BestPlaces Comfort Index for O'Fallon is 7.2 (10=best), which means it is one of the most pleasant places in Illinois.
7.2 / 10
September, May and October are the most pleasant months in O'Fallon, while January and December are the least comfortable months.
Great FallsThe annual BestPlaces Comfort Index for Great Falls is 6.8 (10=best), which means it is more comfortable than most places in Montana.
6.8 / 10
July, August and June are the most pleasant months in Great Falls, while January and December are the least comfortable months.
Today's Weather - Great Falls, MT
3 AM PST
Partly Cloudy
38°F
| DAY | DESCRIPTION | HIGH / LOW | WIND |
|---|
| Overnight | Partly Cloudy | 35° / 65° | SW 3 mph |
| Tuesday Night | Slight Chance Showers And Thunderstorms then Mostly Cloudy | 41° / 60° | SSW 3 to 9 mph |
| Wednesday Night | Showers And Thunderstorms | 40° / 53° | NNE 8 to 14 mph |
| Thursday Night | Slight Chance Light Rain then Partly Cloudy | 36° / 66° | SW 7 mph |
| Friday Night | Mostly Cloudy | 43° / 65° | SW 6 to 10 mph |
| Saturday Night | Chance Rain | 39° / 61° | WSW 12 mph |
| Sunday Night | Slight Chance Light Rain then Partly Cloudy | 40° / 71° | WSW 7 to 12 mph |
Today's Weather - O'Fallon, IL
3 AM PST
Mostly Clear
67°F
| DAY | DESCRIPTION | HIGH / LOW | WIND |
|---|
| Overnight | Mostly Clear | 67° / 91° | S 7 mph |
| Tuesday Night | Showers And Thunderstorms Likely then Showers And Thunderstorms | 64° / 78° | SW 8 to 22 mph |
| Wednesday Night | Showers And Thunderstorms Likely | 63° / 81° | N 3 to 7 mph |
| Thursday Night | Chance Showers And Thunderstorms | 65° / 82° | SE 6 mph |
| Friday Night | Showers And Thunderstorms Likely then Chance Showers And Thunderstorms | 67° / 84° | SW 5 to 8 mph |
| Saturday Night | Chance Showers And Thunderstorms | 66° / 83° | SE 7 mph |
| Sunday Night | Showers And Thunderstorms Likely then Chance Showers And Thunderstorms | 65° / 83° | SW 6 to 9 mph |
Average Monthly High / Low (°F)
| Month | Great Falls, MT | O'Fallon, IL |
|---|
| January | 37° / 17° | 41° / 22° |
| February | 40° / 17° | 46° / 26° |
| March | 48° / 24° | 57° / 34° |
| April | 58° / 33° | 68° / 45° |
| May | 67° / 41° | 77° / 55° |
| June | 76° / 49° | 86° / 63° |
| July | 85° / 54° | 89° / 67° |
| August | 84° / 53° | 88° / 65° |
| September | 72° / 44° | 81° / 56° |
| October | 60° / 35° | 70° / 45° |
| November | 45° / 25° | 57° / 35° |
| December | 36° / 17° | 43° / 25° |
Hot, Freezing, Rainy, Snowy Days: Great Falls / O'Fallon
| Month | Hot Days | Freezing Days | Rainy Days | Snowy Days |
|---|
| January | 0 / 0 | 26 / 26 | 6 / 7 | 6 / 3 |
| February | 0 / 0 | 25 / 21 | 6 / 7 | 6 / 2 |
| March | 0 / 0 | 24 / 14 | 8 / 9 | 6 / 1 |
| April | 0 / 0 | 14 / 3 | 9 / 10 | 4 / 0 |
| May | 0 / 1 | 3 / 0 | 11 / 11 | 1 / 0 |
| June | 1 / 9 | 0 / 0 | 12 / 9 | 0 / 0 |
| July | 9 / 14 | 0 / 0 | 7 / 7 | 0 / 0 |
| August | 8 / 12 | 0 / 0 | 7 / 7 | 0 / 0 |
| September | 2 / 4 | 1 / 0 | 7 / 7 | 1 / 0 |
| October | 0 / 0 | 11 / 3 | 6 / 8 | 2 / 0 |
| November | 0 / 0 | 21 / 12 | 6 / 8 | 5 / 0 |
| December | 0 / 0 | 26 / 23 | 6 / 8 | 6 / 2 |
July is the hottest month for Great Falls with an average high temperature of 85.3°, which ranks it as warmer than most places in Montana. In Great Falls, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Great Falls are June, September and August.
July is the hottest month for O'Fallon with an average high temperature of 89.2°, which ranks it as one of the hottest places in Illinois. In O'Fallon, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for O'Fallon are May, September and October.
January has the coldest nighttime temperatures for Great Falls with an average of 16.6°. This is warmer than most places in Montana.
January has the coldest nighttime temperatures for O'Fallon with an average of 22.0°. This is warmer than most places in Illinois.
In Great Falls, there are 20.9 days annually when the high temperature is over 90°, which is hotter than most places in Montana.
In O'Fallon, there are 39.8 days annually when the high temperature is over 90°, which is one of the hottest places in Illinois.
In Great Falls, there are 151.3 days annually when the nighttime low temperature falls below freezing, which is one of the warmest places in Montana.
In O'Fallon, there are 101.4 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Illinois.
In Great Falls, there are 16.6 days annually when the nighttime low temperature falls below zero°, which is about average compared to other places in Montana.
In O'Fallon, there are 1.6 days annually when the nighttime low temperature falls below zero°, which is one of the warmest places in Illinois.
June is the wettest month in Great Falls with 2.5 inches of rain, and the driest month is January with 0.5 inches. The wettest season is Autumn with 38% of yearly precipitation and 10% occurs in Spring, which is the driest season. The annual rainfall of 14.4 inches in Great Falls means that it is about average compared to other places in Montana.
May is the wettest month in O'Fallon with 4.9 inches of rain, and the driest month is February with 2.4 inches. The wettest season is Summer with 28% of yearly precipitation and 18% occurs in Spring, which is the driest season. The annual rainfall of 43.1 inches in O'Fallon means that it is wetter than most places in Illinois.
June is the rainiest month in Great Falls with 11.5 days of rain, and November is the driest month with only 5.6 rainy days. There are 89.8 rainy days annually in Great Falls, which is about average compared to other places in Montana. The rainiest season is Summer when it rains 30% of the time and the driest is Spring with only a 20% chance of a rainy day.
May is the rainiest month in O'Fallon with 10.9 days of rain, and February is the driest month with only 6.6 rainy days. There are 96.4 rainy days annually in O'Fallon, which is one of the least rainy places in Illinois. The rainiest season is Summer when it rains 30% of the time and the driest is Spring with only a 22% chance of a rainy day.
An annual snowfall of 58.0 inches in Great Falls means that it is snowier than most places in Montana.
An annual snowfall of 11.6 inches in O'Fallon means that it is less snowy than most places in Illinois.
March is the snowiest month in Great Falls with 10.4 inches of snow, and 9 months of the year have significant snowfall.
January is the snowiest month in O'Fallon with 3.8 inches of snow, and 4 months of the year have significant snowfall.
DID YOU KNOW?
Many people confuse Weather and Climate, but they are different. Weather refers to the conditions of the atmosphere over a short period of time, while Climate refers to the conditions of the atmosphere over a long period of time.
Weather, more specifically, refers to how the atmosphere behaves and its effects on life and human activities. Most people think of Weather in terms of what can be observed: temperature, humidity, precipitation, and cloudy/sunny conditions. Weather conditions constantly change on a minute-to-minute basis.
Climate is a record of the average weather conditions for a given place over a long period of time, often referred to as Climate Normals. A 30-year period of record is a common requirement to be considered a Climate Normal.
Reviews for Great Falls 
2 Reviews
Hi. I'd like to know if you still feel the same way about living in Broomfield. I went there this past July to check it out (along with Lafayette, Boulder (can't More
Apex is perfect for what you are looking for. It's close enough to Raleigh, Durham, Chapel Hill to find a job and Cary the next town over, is a little more expensive but More
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Reviews for O'fallon 2 Reviews
Hi. I'd like to know if you still feel the same way about living in Broomfield. I went there this past July to check it out (along with Lafayette, Boulder (can't More
Apex is perfect for what you are looking for. It's close enough to Raleigh, Durham, Chapel Hill to find a job and Cary the next town over, is a little more expensive but More
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