The climate of the Sacramento Valley (north Central Valley) and San Joaquin Valley are very different. The Sacramento Valley has a "Mediterranean climate". This means that it has warm, dry summers and cool, wet winters. The San Joaquin Valley is much hotter and drier. Most of it is "Mediterranean steppe", which is similar to Mediterranean except that it is warmer and drier. Some of it, however, can be close to desert climate. This section of the Central Valley is said to have the worst air quality in California.