The Central Valley can get very foggy in winter, making driving extremely dangerous with visibility of 100 feet and less. On the faster highways such as Interstate 5 and State Route 99, the fog can turn small accidents into smash-ups of dozens of cars.
Gang activity is quite common in the larger cities. Avoid being out alone after dark, and avoid wearing solid red or solid blue, as these are gang colors and may make you a target.
San Joaquin cities such as Bakersfield, Fresno, Visalia, Merced, and Modesto have very bad air quality. In fact, all of these cities rank among the top 15 smoggiest cities in the U.S. Summer temperatures can soar above 110°F 45°C. Drink lots of water, heat strokes and dehydration is very common during the summer.
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English and Spanish are both spoken in the San Joaquin Valley. It's helpful to know a little of each, as many people speak only one or the other. Punjabi and Tagalog are also widely spoken by Indian and Filipino immigrants in major cities.