2025 Compare Climate & Weather:
Portola Valley, CA vs Ann Arbor, MI

Highlights

On average, there are 178 sunny days per year in Ann Arbor. Portola Valley averages 262 sunny days per year. The US average is 205 sunny days.

Ann Arbor, Michigan gets 36 inches of rain, on average, per year. Portola Valley, California gets 30.7 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

Ann Arbor averages 43 inches of snow per year. Portola Valley averages 0 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

Ann Arbor, Michigan
Summer High: the July high is around 82.8 degrees
Winter Low: the January low is 16.5
Rain: averages 36 inches of rain a year
Snow: averages 43 inches of snow a year

Portola Valley, California
Summer High: the July high is around 77.2 degrees
Winter Low: the January low is 40.8
Rain: averages 30.7 inches of rain a year
Snow: averages 0 inches of snow a year

BestPlaces Comfort Index

The annual BestPlaces Comfort Index for Ann Arbor is 6.7 (10=best), which means it is more comfortable than most places in Michigan.

The annual BestPlaces Comfort Index for Portola Valley is 8.4 (10=best), which means it is more comfortable than most places in California.

Today's Weather - Ann Arbor, MI

58°F

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: Portola Valley / Ann Arbor

August is the hottest month for Portola Valley with an average high temperature of 77.6°, which ranks it as cooler than most places in California. In Portola Valley, there are 6 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Portola Valley are August, September and July.

July is the hottest month for Ann Arbor with an average high temperature of 82.8°, which ranks it as warmer than most places in Michigan. In Ann Arbor, there are 4 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Ann Arbor are June, August and September.

December has the coldest nighttime temperatures for Portola Valley with an average of 40.7°. This is warmer than most places in California.

January has the coldest nighttime temperatures for Ann Arbor with an average of 16.5°. This is warmer than most places in Michigan.

In Portola Valley, there are 19.7 days annually when the high temperature is over 90°, which is cooler than most places in California.

In Ann Arbor, there are 5.8 days annually when the high temperature is over 90°, which is about average compared to other places in Michigan.

In Portola Valley, there are 14.8 days annually when the nighttime low temperature falls below freezing, which is about average compared to other places in California.

In Ann Arbor, there are 140.9 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Michigan.

In Portola Valley, there are 0.0 days annually when the nighttime low temperature falls below zero°, which is about average compared to other places in California.

In Ann Arbor, there are 3.9 days annually when the nighttime low temperature falls below zero°, which is warmer than most places in Michigan.

February is the wettest month in Portola Valley with 6.0 inches of rain, and the driest month is July with 0.0 inches. The wettest season is Spring with 58% of yearly precipitation and 1% occurs in Autumn, which is the driest season. The annual rainfall of 30.7 inches in Portola Valley means that it is wetter than most places in California.


June is the wettest month in Ann Arbor with 3.7 inches of rain, and the driest month is February with 2.2 inches. The wettest season is Autumn with 30% of yearly precipitation and 20% occurs in Spring, which is the driest season. The annual rainfall of 36.0 inches in Ann Arbor means that it is wetter than most places in Michigan.

February is the rainiest month in Portola Valley with 11.2 days of rain, and July is the driest month with only 1.0 rainy days. There are 72.9 rainy days annually in Portola Valley, which is rainier than most places in California. The rainiest season is Spring when it rains 45% of the time and the driest is Autumn with only a 6% chance of a rainy day.

December is the rainiest month in Ann Arbor with 13.9 days of rain, and September is the driest month with only 9.6 rainy days. There are 136.9 rainy days annually in Ann Arbor, which is rainier than most places in Michigan. The rainiest season is Spring when it rains 28% of the time and the driest is Autumn with only a 23% chance of a rainy day.

There is rarely any recorded snowfall in Portola Valley, ranking it as one of the least snowy places in California.

An annual snowfall of 43.0 inches in Ann Arbor means that it is less snowy than most places in Michigan.

Any measurable snowfall is a rare occurance in Portola Valley.

January is the snowiest month in Ann Arbor with 12.4 inches of snow, and 6 months of the year have significant snowfall.