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The climate of the Southeast is uniquely warm <br />and wet, with mild winters and high humidity, <br />compared with the rest of the continental United <br />States. The average annual temperature of the <br />Southeast did not change significantly over the <br />past century as a whole. Since 1970, however, <br />annual average temperature has risen about 2 °F, <br />with the greatest seasonal increase in tempera- <br />ture occurring during the winter months. The <br />number of freezing days in the Southeast has <br />declined by four to seven days per year for most <br />of the region since the mid- 1970s. <br />Average autumn precipitation has increased <br />by 30 percent for the region since 1901. The <br />decline in fall precipitation in South Florida <br />contrasts strongly with the regional average. <br />There has been an increase in heavy downpours <br />in many parts of the region,"o,ssi while the <br />percentage of the region experiencing moder- <br />ate to severe drought increased over the past <br />three decades. The area of moderate to severe <br />spring and summer drought has increased by 12 <br />percent and 14 percent, respectively, since the mid - <br />1970s. Even in the fall months, when precipitation <br />tended to increase in most of the region, the extent <br />of drought increased by 9 percent. <br />Climate models project continued warming in all <br />seasons across the Southeast and an increase in <br />the rate of warming through the end of this cen- <br />tury. The projected rates <br />of warming are more than <br />double those experienced <br />in the Southeast since 1975, <br />with the greatest tempera- <br />ture increases projected <br />to occur in the summer <br />months. The number of very <br />hot days is projected to rise <br />at a greater rate than the av- <br />erage temperature. Under a <br />lower emissions scenario,91 <br />­40, ,4 -10 •25 ,,,20 05 00 , -5 0 5 90 $5 20 25 30 35 -4 <br />Pol,reM Mange, N�DAA/NICIDC 382 <br />average temperatures in the region are projected <br />to rise by about 4.5 °F by the 2080s, while a higher <br />emissions scenario 91 yields about 9 °F of average <br />warming (with about a 10.5 °F increase in summer, <br />and a much higher heat index). Spring and sum- <br />mer rainfall is projected to decline in South Florida <br />during this century. Except for indications that <br />the amount of rainfall from individual hurricanes <br />will increase '61 climate models provide divergent <br />Observed temperature and precipitation changes in the Southeast are summarized above for two <br />different period S.313 Southeast average temperature declined from 1901 to 1970 and then increased <br />strongly since 1970. <br />01 <br />Temperature Change in °F <br />Precipitation change in <br />1901 -2008 <br />1970 -2008 <br />1901 -2008 <br />1970 -2008 <br />Annual <br />0.3 <br />1.6 <br />Annual <br />6.0 <br />-7.7 <br />Winter <br />0.2 <br />2.7 <br />Winter <br />1.2 <br />-9.6 <br />Spring <br />0.4 <br />1.2 <br />Spring <br />1.7 <br />-29.2 <br />Summer <br />0.4 <br />1.6 <br />Summer <br />-4.0 <br />3.6 <br />Fall <br />0.2 <br />1.1 <br />Fall <br />27.4 <br />0.1 <br />Observed temperature and precipitation changes in the Southeast are summarized above for two <br />different period S.313 Southeast average temperature declined from 1901 to 1970 and then increased <br />strongly since 1970. <br />01 <br />