I largely agree with the previous two posters regarding their insights on the weather in Madison, WI, however, I just have to add a caveat of sorts - Madison's (or Milwaukee metro's...the area I know that you are interested in living via your other post) winters aren't as bad as say - the Upper Penninsula or upstate NY. But having said that, that is like saying Phoenix's summers aren't that hot...(if you are comparing it to Death Valley). While I am not certain the portion of Cali you would be coming from, assuming it is any of the fairly large, common metro areas (and not a high altitude area of Cali), you will indeed be in for a very large adjustment as it relates to the winters.
First off, let me state that to me (my standard of comparison in the Milwaukee metro area...roughly the warmest overall winter area in the state - [yet still freezing cold in winter]) the hardest part about winter is NOT the intense cold or snow of Dec.-Feb. Rather, the hardest part is the length of the winter.
Essentially, winter is a Thanksgiving through April Fool's Day season here, if not a hare longer. March and April are tough months in general, as while in most parts of the nation you expect chilly or cold weather in Dec. - Feb., other parts of the nation get much more of a gradual warm up in March and April than we do in WI; we are one of the last areas (the Upper Midwest in general) to get that springtime warmup.
Here on September 12, we are coming off of a night where there were warnings for areas of patchy frost. So you can feel a decent chill in the air from September through May in SE WI.
As for the heart of winter, snows may and do vary from year-to-year. Some folks do have a bit of a skewed perception of how "snowy it used to be" and now "how little snow we get"...memories of weather tend to get fuzzy that way. If you look at the actual snow stats, winter snowfalls in SE WI always have been kind of up and down. This past winter was especially snowy in Milwaukee, with the Brew City picking up approximately 60 inches of snowfall...first major snowfall was in early December (approx. 8 inches) and last major snowfall was in mid-April (approx. 8 inches) - yes, snow in April, especially of that magnitude, is very rare here.
The winter of 2000 saw 40+ inches of snow fall in December - again, that was an aberration but it happens.
In general, you could count on likely anywhere between 25 to 60 inches of snowfall in a winter. Roughly the same snowfall amount on average that Denver, CO receives, however, unlike Denver, the snowfall here melts much less briskly. Having said that, snow removal here is very quick and efficient.
December through February are very cold months, especially when compared to most of Cali. Many, many days do not even ever get above freezing (32 degrees) for a high, and there likely will be a patch of days where the high is only 10 - 15 degrees.
Temperature averages in winter from the Weather Channel (
National and Local Weather Forecast, Radar, Map and Report) -
November: AVE HIGH 46 / AVE LOW 31
December: AVE HIGH 33 / AVE LOW 19
January: AVE HIGH 27 / AVE LOW 13
February: AVE HIGH 32 / AVE LOW 18
March: AVE HIGH 42 / AVE LOW 27
See the whole year average for yourself:
Average Weather for Milwaukee, WI - Temperature and Precipitation
So is winter cold? Check. Long? Check. Snowy? Check, although admittedly that varies quite a bit from year-to-year.
What else is bad about it? The grayness. This is where a Denver winter has a Milwaukee/Chicago winter beat...whereas Denver is cold and snowy in the winter, it is also generally still sunny. Here, from November through March, you'll see the sun...some days (maybe 40% of the time is a good average). However, many, many days are thick gray.
Have I sufficiently depressed you enough?

Not trying to. I just lived for 4 years in one of the great American climates - Albuquerque, NM - and relocated back to metro Milwaukee; why? it is a great place to live, regardless of the winters. I have often heard it said that if it weren't for the winters, Milwaukee would be one of the best cities in the US.
But, especially with you coming from Cali, you do need to know what you are in for winter-wise. It is indeed one of the significant drawbacks to living here for most people.
Now...remember, Chicago (3rd biggest city in US...9+ millions people metro), Twin Cities (3+ million metro - quickly growing), metro Detroit (5+ million people metro), Cleveland (2 million people metro), Indianapolis (2 million people metro), etc., etc., etc., join Milwaukee (2 million people metro) in sharing these winter "delights"...so it isn't like Milwaukeeans are alone in their winter sufferings. I guess if not "misery loves company", what I am trying to convey is that a huge chunk of the US population lives with it and deals with it yearly, so it isn't like only Milwaukeeans encumber these winter sufferings. People do do it!
I should also state that the trade off for the bad 6 months of weather here is that there are 6 great months of weather here. Summers are very pleasant and mild (Milwaukee averages only 9 days per year where it hits 90 degrees or more), and falls are quite picturesque and pleasant...late springs very nice too.
Metro Milwaukee is a great area and a great place to live. If you can suck it up for the 6 bad months of weather - maybe plan one or two getaway trips during this time to knock it down more to 5 months - then relish the 6 great months of weather, you'll really be okay because lots of other things here make up for the weather!