Climate model estimates of the potential impact of increases in radiatively-active trace gases in the atmosphere suggest that the globe will likely experience a warming of 1-4o C, with attendant increases in the vigor of the hydrologic cycle over the next century. Much of this change will likely manifest itself in the form of increases in the frequency of extreme events. In this paper observed trends in global and U.S. temperature and precipitation will be discussed, both in terms of mean values and extreme temperature and precipitation events. Recent work indicates that 10 of the last 15 years (through 1997) have been the warmest global temperatures on record, and that North America has experienced a precipitation increase of 10-20% over the 20th century. In the U.S. and other countries much of the precipitation increase can be attributed to increases in heavy and extreme precipitation events. These increases have occurred in both single-day and multi-day precipitation events. Lastly, the U.S. has experienced a significant decline in the number of days where the temperature dips below freezing, particularly in the spring. This appears to be related to recently observed decreases in spring snow cover over North America