http://en.wikipedia.org/wiki/Sacramento,_California
It has high winter temperatures and high summer temperatures too.
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asked Jun 26, 2014 at 19:48
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6$\begingroup$ Redding, CA (at the north end of the Sacramento valley) is even warmer in the summer. Low elevation, foehn winds, no continental polar air mass intrusions, placement of the Pacific semi-permanent high pressure, and high pressure retrograding from the Great Basin are the key factors. Temperatures in Sacramento vary greatly depending on the direction of the winds. Onshore flow can drop temperatures by 20+ degrees (the "delta breeze"). Offshore flow in the summer is often triple digits. $\endgroup$– DrewP84Commented Jun 26, 2014 at 22:22
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2$\begingroup$ Redding is even warmer than Sacramento because the city experiences increased warming from foehn winds (simply called "the north wind" locally) and has less interaction with the cooler marine airmass since there are no breaks in the Coastal range that far north. $\endgroup$– DrewP84Commented Jun 26, 2014 at 22:30
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2$\begingroup$ This image shows air masses in the USA. Continental Polar is the coolest and impacts most locations in the USA at this latitude. Maritime Tropical(year round) and occasionally Continental Tropical(summer)/Maritime Polar(winter) impact Sacramento but never Continental Polar. $\endgroup$– DrewP84Commented Jun 27, 2014 at 1:08
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2$\begingroup$ @DrewP84 why not adding that as an answer? $\endgroup$– plannapusCommented Jun 28, 2014 at 14:43
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$\begingroup$ Don't forget the urban heat island effect too! $\endgroup$– f.thorpe ♦Commented Jul 2, 2014 at 16:28
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1 Answer
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The main reason for Sacramento's warmth compared to some other cities at the same latitude is, like in many cases, due to the city's surrounding topography, as can be seen in the topographic map below:
Source: Wikipedia: Geography of California
In regards to the climate of Sacramento, it is probably better to consider why it is seasonally warmer than cities on the same latitude.
Sacramento is located in a regionally low elevation Great Valley (also Central Valley) (1), in between two roughly parallel mountains ranges that converge in the north of the Valley in the Klamath Ranges. The Coastal Range on the west and the Sierra Nevada to the east (2).
The Köppen climate classification for Sacramento is Csa, which is defined as a Mediterranean environment with hot summers (1). The Coastal Range largely shields the city (and the Valley) from the climate (especially much of the humidity) of the Maritime climate to the west, and the Continental climate to the east (2). Essentially, according to the WRCC, the climate of the Valley (including Sacramento) is intermediate between the climates either side of the bordering ranges (2).
The very cold winters that can occur in the Continental climate are blocked by the Sierra Nevada. Even if cold air does get over the mountain, the air warms as it compresses as descends into the Valley, and hence is milder when it reaches the Valley (2).
In regards to the Urban Heat Island, The US EPA (3) performed measurements and observations of Sacramento between 1998-2002, revealing that there is an urban heat island of the order of an average increase in temperature in the city of 0.5-1°C (0.9-1.8°F) compared to the surrounding non-urban areas.
References
(1) Kauffman, E. Climate and Topography California Department of Fish and Wildlife
(2) Western Regional Climate Centre (WRCC), Climate of California
(3) U.S. EPA Urban Heat Island Pilot Project: Profile of Sacramento