2025 Compare Climate & Weather:
O'Fallon, IL vs Medical Lake, WA

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Highlights

On average, there are 171 sunny days per year in Medical Lake. O'Fallon averages 202 sunny days per year. The US average is 205 sunny days.

Medical Lake, Washington gets 17.5 inches of rain, on average, per year. O'Fallon, Illinois gets 43.1 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

Medical Lake averages 44.4 inches of snow per year. O'Fallon averages 11.6 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

Medical Lake, Washington
Summer High: the July high is around 82.7 degrees
Winter Low: the January low is 23
Rain: averages 17.5 inches of rain a year
Snow: averages 44.4 inches of snow a year

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

BestPlaces Comfort Index

Medical Lake

The annual BestPlaces Comfort Index for Medical Lake is 6.7 (10=best), which means it is less comfortable than most places in Washington.

6.7 / 10

July, August and June are the most pleasant months in Medical Lake, while December and January are the least comfortable months.

O'Fallon

The 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.

Average Monthly High / Low (°F)

Month	O'Fallon, IL	Medical Lake, WA
January	41° / 22°	34° / 23°
February	46° / 26°	40° / 24°
March	57° / 34°	49° / 30°
April	68° / 45°	57° / 35°
May	77° / 55°	66° / 41°
June	86° / 63°	73° / 47°
July	89° / 67°	83° / 51°
August	88° / 65°	83° / 50°
September	81° / 56°	73° / 42°
October	70° / 45°	58° / 34°
November	57° / 35°	42° / 28°
December	43° / 25°	33° / 21°

Hot, Freezing, Rainy, Snowy Days: O'Fallon / Medical Lake

Month	Hot Days	Freezing Days	Rainy Days	Snowy Days
January	0 / 0	26 / 25	7 / 12	3 / 8
February	0 / 0	21 / 24	7 / 9	2 / 5
March	0 / 0	14 / 20	9 / 11	1 / 4
April	0 / 0	3 / 10	10 / 9	0 / 1
May	1 / 0	0 / 3	11 / 10	0 / 0
June	9 / 1	0 / 0	9 / 8	0 / 0
July	14 / 5	0 / 0	7 / 4	0 / 0
August	12 / 6	0 / 0	7 / 4	0 / 0
September	4 / 1	0 / 4	7 / 5	0 / 0
October	0 / 0	3 / 12	8 / 8	0 / 0
November	0 / 0	12 / 21	8 / 13	0 / 4
December	0 / 0	23 / 28	8 / 13	2 / 9

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.

August is the hottest month for Medical Lake with an average high temperature of 82.9°, which ranks it as warmer than most places in Washington. In Medical Lake, there are 4 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Medical Lake are July, September and August.

January has the coldest nighttime temperatures for O'Fallon with an average of 22.0°. This is warmer than most places in Illinois.

December has the coldest nighttime temperatures for Medical Lake with an average of 20.9°. This is one of the coldest places in Washington.

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 Medical Lake, there are 13.4 days annually when the high temperature is over 90°, which is hotter than most places in Washington.

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 Medical Lake, there are 145.1 days annually when the nighttime low temperature falls below freezing, which is colder than most places in Washington.

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.

In Medical Lake, there are 2.6 days annually when the nighttime low temperature falls below zero°, which is one of the coldest places in Washington.

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.

December is the wettest month in Medical Lake with 2.7 inches of rain, and the driest month is August with 0.5 inches. The wettest season is Spring with 34% of yearly precipitation and 14% occurs in Autumn, which is the driest season. The annual rainfall of 17.5 inches in Medical Lake means that it is drier than most places in Washington.

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.

December is the rainiest month in Medical Lake with 12.6 days of rain, and August is the driest month with only 3.5 rainy days. There are 102.8 rainy days annually in Medical Lake, which is less rainy than most places in Washington. The rainiest season is Spring when it rains 33% of the time and the driest is Autumn with only a 14% chance of a rainy day.

An annual snowfall of 11.6 inches in O'Fallon means that it is less snowy than most places in Illinois.

An annual snowfall of 44.4 inches in Medical Lake means that it is one of the snowiest places in Washington.

January is the snowiest month in O'Fallon with 3.8 inches of snow, and 4 months of the year have significant snowfall.

December is the snowiest month in Medical Lake with 14.3 inches of snow, and 6 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 O'fallon 2 Reviews

Jill · Sherman Oaks, CA

re:

Over 16 years ago

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

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NC For Me · Apex, NC

re:

Over 16 years ago

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

| Reply

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Reviews for Medical Lake 2 Reviews

Jill · Sherman Oaks, CA

re:

Over 16 years ago

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

| Reply

NC For Me · Apex, NC

re:

Over 16 years ago

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

| Reply

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2025 Compare Climate & Weather:
O'Fallon, IL vs Medical Lake, WA

Highlights

Weather Highlights

BestPlaces Comfort Index

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: O'Fallon / Medical Lake

January has the coldest nighttime temperatures for O'Fallon with an average of 22.0°. This is warmer than most places in Illinois.

December has the coldest nighttime temperatures for Medical Lake with an average of 20.9°. This is one of the coldest places in Washington.

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 Medical Lake, there are 13.4 days annually when the high temperature is over 90°, which is hotter than most places in Washington.

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 Medical Lake, there are 145.1 days annually when the nighttime low temperature falls below freezing, which is colder than most places in Washington.

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.

In Medical Lake, there are 2.6 days annually when the nighttime low temperature falls below zero°, which is one of the coldest places in Washington.

An annual snowfall of 11.6 inches in O'Fallon means that it is less snowy than most places in Illinois.

An annual snowfall of 44.4 inches in Medical Lake means that it is one of the snowiest places in Washington.

January is the snowiest month in O'Fallon with 3.8 inches of snow, and 4 months of the year have significant snowfall.

December is the snowiest month in Medical Lake with 14.3 inches of snow, and 6 months of the year have significant snowfall.

DID YOU KNOW?

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2025 Compare Climate & Weather:O'Fallon, IL vs Medical Lake, WA

Highlights

Weather Highlights

BestPlaces Comfort Index

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: O'Fallon / Medical Lake

January has the coldest nighttime temperatures for O'Fallon with an average of 22.0°. This is warmer than most places in Illinois.December has the coldest nighttime temperatures for Medical Lake with an average of 20.9°. This is one of the coldest places in Washington.

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 Medical Lake, there are 13.4 days annually when the high temperature is over 90°, which is hotter than most places in Washington.

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 Medical Lake, there are 145.1 days annually when the nighttime low temperature falls below freezing, which is colder than most places in Washington.

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.In Medical Lake, there are 2.6 days annually when the nighttime low temperature falls below zero°, which is one of the coldest places in Washington.

An annual snowfall of 11.6 inches in O'Fallon means that it is less snowy than most places in Illinois.An annual snowfall of 44.4 inches in Medical Lake means that it is one of the snowiest places in Washington.

January is the snowiest month in O'Fallon with 3.8 inches of snow, and 4 months of the year have significant snowfall.December is the snowiest month in Medical Lake with 14.3 inches of snow, and 6 months of the year have significant snowfall.

DID YOU KNOW?

Reviews for O'fallon 2 Reviews

Reviews for Medical Lake 2 Reviews

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Zips In O'Fallon, Illinois

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2025 Compare Climate & Weather:
O'Fallon, IL vs Medical Lake, WA

January has the coldest nighttime temperatures for O'Fallon with an average of 22.0°. This is warmer than most places in Illinois.

December has the coldest nighttime temperatures for Medical Lake with an average of 20.9°. This is one of the coldest places in Washington.

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 Medical Lake, there are 13.4 days annually when the high temperature is over 90°, which is hotter than most places in Washington.

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 Medical Lake, there are 145.1 days annually when the nighttime low temperature falls below freezing, which is colder than most places in Washington.

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.

In Medical Lake, there are 2.6 days annually when the nighttime low temperature falls below zero°, which is one of the coldest places in Washington.

An annual snowfall of 11.6 inches in O'Fallon means that it is less snowy than most places in Illinois.

An annual snowfall of 44.4 inches in Medical Lake means that it is one of the snowiest places in Washington.

January is the snowiest month in O'Fallon with 3.8 inches of snow, and 4 months of the year have significant snowfall.

December is the snowiest month in Medical Lake with 14.3 inches of snow, and 6 months of the year have significant snowfall.