2025 Compare Climate & Weather:
Groton, CT vs Keystone, SD

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Highlights

On average, there are 222 sunny days per year in Keystone. Groton averages 204 sunny days per year. The US average is 205 sunny days.

Keystone, South Dakota gets 20.1 inches of rain, on average, per year. Groton, Connecticut gets 47.9 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

Keystone averages 54.1 inches of snow per year. Groton averages 26.6 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

Keystone, South Dakota
Summer High: the July high is around 81.2 degrees
Winter Low: the January low is 12.1
Rain: averages 20.1 inches of rain a year
Snow: averages 54.1 inches of snow a year

Groton, Connecticut
Summer High: the July high is around 79.6 degrees
Winter Low: the January low is 21.7
Rain: averages 47.9 inches of rain a year
Snow: averages 26.6 inches of snow a year

BestPlaces Comfort Index

Keystone

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

6.7 / 10

August, July and June are the most pleasant months in Keystone, while February and December are the least comfortable months.

Groton

The annual BestPlaces Comfort Index for Groton is 7.1 (10=best), which means it is more comfortable than most places in Connecticut.

7.1 / 10

June, September and August are the most pleasant months in Groton, while January and February are the least comfortable months.

Average Monthly High / Low (°F)

Month	Groton, CT	Keystone, SD
January	38° / 22°	39° / 12°
February	40° / 24°	40° / 13°
March	47° / 30°	46° / 20°
April	56° / 39°	54° / 28°
May	66° / 48°	63° / 38°
June	74° / 58°	73° / 46°
July	80° / 64°	81° / 52°
August	79° / 63°	80° / 50°
September	73° / 56°	71° / 40°
October	62° / 44°	59° / 30°
November	53° / 37°	46° / 20°
December	43° / 27°	38° / 12°

Hot, Freezing, Rainy, Snowy Days: Groton / Keystone

Month	Hot Days	Freezing Days	Rainy Days	Snowy Days
January	0 / 0	26 / 30	10 / 5	4 / 4
February	0 / 0	23 / 27	9 / 5	3 / 4
March	0 / 0	19 / 28	11 / 7	2 / 5
April	0 / 0	4 / 21	11 / 10	0 / 4
May	0 / 0	0 / 7	11 / 12	0 / 1
June	0 / 1	0 / 1	10 / 12	0 / 0
July	1 / 5	0 / 0	9 / 11	0 / 0
August	0 / 3	0 / 0	9 / 9	0 / 0
September	0 / 1	0 / 4	9 / 7	0 / 0
October	0 / 0	2 / 18	9 / 7	0 / 2
November	0 / 0	10 / 27	10 / 4	0 / 3
December	0 / 0	22 / 31	11 / 4	2 / 4

July is the hottest month for Groton with an average high temperature of 79.6°, which ranks it as one of the coolest places in Connecticut. In Groton, there are 4 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Groton are August, July and June.

July is the hottest month for Keystone with an average high temperature of 81.2°, which ranks it as one of the coolest places in South Dakota. In Keystone, there are 4 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Keystone are August, July and June.

January has the coldest nighttime temperatures for Groton with an average of 21.7°. This is one of the warmest places in Connecticut.

December has the coldest nighttime temperatures for Keystone with an average of 11.6°. This is warmer than most places in South Dakota.

In Groton, there are 1.7 days annually when the high temperature is over 90°, which is one of the coolest places in Connecticut.

In Keystone, there are 9.3 days annually when the high temperature is over 90°, which is cooler than most places in South Dakota.

In Groton, there are 106.2 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Connecticut.

In Keystone, there are 194.3 days annually when the nighttime low temperature falls below freezing, which is one of the coldest places in South Dakota.

In Groton, there are 0.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in Connecticut.

In Keystone, there are 17.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in South Dakota.

March is the wettest month in Groton with 4.7 inches of rain, and the driest month is February with 3.1 inches. The wettest season is Summer with 27% of yearly precipitation and 22% occurs in Spring, which is the driest season. The annual rainfall of 47.9 inches in Groton means that it is drier than most places in Connecticut.

May is the wettest month in Keystone with 3.7 inches of rain, and the driest month is January with 0.3 inches. The wettest season is Autumn with 41% of yearly precipitation and 6% occurs in Spring, which is the driest season. The annual rainfall of 20.1 inches in Keystone means that it is drier than most places in South Dakota.

May is the rainiest month in Groton with 11.4 days of rain, and August is the driest month with only 8.8 rainy days. There are 118.6 rainy days annually in Groton, which is about average compared to other places in Connecticut. The rainiest season is Summer when it rains 28% of the time and the driest is Autumn with only a 23% chance of a rainy day.

May is the rainiest month in Keystone with 11.6 days of rain, and November is the driest month with only 4.2 rainy days. There are 90.9 rainy days annually in Keystone, which is one of the rainiest places in South Dakota. The rainiest season is Autumn when it rains 34% of the time and the driest is Spring with only a 15% chance of a rainy day.

An annual snowfall of 26.6 inches in Groton means that it is less snowy than most places in Connecticut.

An annual snowfall of 54.1 inches in Keystone means that it is one of the snowiest places in South Dakota.

February is the snowiest month in Groton with 7.8 inches of snow, and 6 months of the year have significant snowfall.

April is the snowiest month in Keystone with 12.1 inches of snow, and 9 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 Groton 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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Reviews for Keystone 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

Start Your Review of Keystone

See all reviews

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2025 Compare Climate & Weather:
Groton, CT vs Keystone, SD

Highlights

Weather Highlights

BestPlaces Comfort Index

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: Groton / Keystone

January has the coldest nighttime temperatures for Groton with an average of 21.7°. This is one of the warmest places in Connecticut.

December has the coldest nighttime temperatures for Keystone with an average of 11.6°. This is warmer than most places in South Dakota.

In Groton, there are 1.7 days annually when the high temperature is over 90°, which is one of the coolest places in Connecticut.

In Keystone, there are 9.3 days annually when the high temperature is over 90°, which is cooler than most places in South Dakota.

In Groton, there are 106.2 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Connecticut.

In Keystone, there are 194.3 days annually when the nighttime low temperature falls below freezing, which is one of the coldest places in South Dakota.

In Groton, there are 0.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in Connecticut.

In Keystone, there are 17.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in South Dakota.

An annual snowfall of 26.6 inches in Groton means that it is less snowy than most places in Connecticut.

An annual snowfall of 54.1 inches in Keystone means that it is one of the snowiest places in South Dakota.

February is the snowiest month in Groton with 7.8 inches of snow, and 6 months of the year have significant snowfall.

April is the snowiest month in Keystone with 12.1 inches of snow, and 9 months of the year have significant snowfall.

DID YOU KNOW?

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Reviews for Keystone 2 Reviews

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2025 Compare Climate & Weather:Groton, CT vs Keystone, SD

Highlights

Weather Highlights

BestPlaces Comfort Index

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: Groton / Keystone

January has the coldest nighttime temperatures for Groton with an average of 21.7°. This is one of the warmest places in Connecticut.December has the coldest nighttime temperatures for Keystone with an average of 11.6°. This is warmer than most places in South Dakota.

In Groton, there are 1.7 days annually when the high temperature is over 90°, which is one of the coolest places in Connecticut.In Keystone, there are 9.3 days annually when the high temperature is over 90°, which is cooler than most places in South Dakota.

In Groton, there are 106.2 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Connecticut.In Keystone, there are 194.3 days annually when the nighttime low temperature falls below freezing, which is one of the coldest places in South Dakota.

In Groton, there are 0.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in Connecticut.In Keystone, there are 17.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in South Dakota.

An annual snowfall of 26.6 inches in Groton means that it is less snowy than most places in Connecticut.An annual snowfall of 54.1 inches in Keystone means that it is one of the snowiest places in South Dakota.

February is the snowiest month in Groton with 7.8 inches of snow, and 6 months of the year have significant snowfall.April is the snowiest month in Keystone with 12.1 inches of snow, and 9 months of the year have significant snowfall.

DID YOU KNOW?

Reviews for Groton 2 Reviews

Reviews for Keystone 2 Reviews

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2025 Compare Climate & Weather:
Groton, CT vs Keystone, SD

January has the coldest nighttime temperatures for Groton with an average of 21.7°. This is one of the warmest places in Connecticut.

December has the coldest nighttime temperatures for Keystone with an average of 11.6°. This is warmer than most places in South Dakota.

In Groton, there are 1.7 days annually when the high temperature is over 90°, which is one of the coolest places in Connecticut.

In Keystone, there are 9.3 days annually when the high temperature is over 90°, which is cooler than most places in South Dakota.

In Groton, there are 106.2 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Connecticut.

In Keystone, there are 194.3 days annually when the nighttime low temperature falls below freezing, which is one of the coldest places in South Dakota.

In Groton, there are 0.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in Connecticut.

In Keystone, there are 17.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in South Dakota.

An annual snowfall of 26.6 inches in Groton means that it is less snowy than most places in Connecticut.

An annual snowfall of 54.1 inches in Keystone means that it is one of the snowiest places in South Dakota.

February is the snowiest month in Groton with 7.8 inches of snow, and 6 months of the year have significant snowfall.

April is the snowiest month in Keystone with 12.1 inches of snow, and 9 months of the year have significant snowfall.