The city lies in the northcentral part of California, not far from Sutter's Mill and the orginal California Gold Rush. The Sacramento and American Rivers flow together here. Summers are hot and dry with July's average 76 degrees. Summer heat is often moderated by a sea breeze known as the "delta breeze" which comes through the Sacramento–San Joaquin River Delta from the San Francisco Bay, and temperatures cool down sharply at night. In winter, the average January temperature is in the low 46 degrees. The foggiest months are December and January with Tule fog that can be extremely dense, lowering visibility to less than 100 feet (30 m) and making driving conditions extremely hazardous. Chilling tule fog events have been known to last for several consecutive days or weeks.