I don't know that it is necessarily based on temperature - but rather it is related to precipitation.
I believe the center of the country, particularly Nebraska, the Dakotas, and E. Montana have been receiving less rain.
However,
http://www.crh.noaa.gov/ict/?n=drought (May 19.)
But I wonder what the temperatures will be like over the next decade.
There was the heat wave last year.
http://en.wikipedia.org/wiki/2006_North_American_heat_wave
Then there is anecdotal stuff like:
or
http://www.crh.noaa.gov/ict/newsletter/Fall2005.php
Summer Climate Summary
Somewhere, like the NCDC at NOAA, there is a temperature record, but finding or accessing it seems to be a challenge.
I found this, but it only gives temperature records for a given day, and not a continuous (with time) dataset.
http://www.crh.noaa.gov/ict/climate/viewrecords.php
Here is some record temperatures near Wichita for July.
Date
July Record High/Record Low/Coolest High/Warmest Low
1 . 109 in 1980 . 58 in 1995 . 71 in 1988 . 78 in 1956
2 . 108 in 1990 . 54 in 1959 . 71 in 1915 . 80 in 1980
3 . 108 in 1990 . 53 in 1924 . 73 in 1892 . 80 in 1897
4 . 110 in 1980 . 53 in 1892 . 72 in 1915 . 80 in 1969
5 . 106 in 1980 . 51 in 1972 . 69 in 1967 . 82 in 1953
6 . 107 in 1980 . 55 in 1972 . 71 in 1904 . 79 in 1966
7 . 106 in 1980 . 55 in 1908 . 68 in 1894 . 80 in 1980
8 . 108 in 1980 . 55 in 1952 . 70 in 1896 . 82 in 1980
9 . 110 in 1980 . 55 in 1905 . 71 in 1905 . 83 in 1980
10 . 110 in 1980 . 53 in 1905 . 64 in 1895 . 81 in 1980
11 . 111 in 1980 . 55 in 1905 . 69 in 1996 . 81 in 1954
12 . 112 in 1980 . 56 in 1975 . 70 in 1953 . 80 in 1980
13 . 111 in 1954 . 51 in 1975 . 72 in 1951 . 80 in 1934
14 . 113 in 1954 . 52 in 1990 . 74 in 1973 . 81 in 1980
15 . 110 in 1936 . 55 in 1990 . 74 in 1891 . 83 in 1936
16 . 110 in 1980 . 57 in 1906 . 66 in 1967 . 82 in 1980
17 . 110 in 1980 . 57 in 1900 . 75 in 1911 . 82 in 1936
18 . 112 in 1936 . 59 in 1911 . 71 in 1967 . 82 in 1936
19 . 109 in 2006 . 61 in 1947 . 76 in 1911 . 82 in 1936
20 . 109 in 2006 . 55 in 1971 . 70 in 1970 . 81 in 1978
21 . 107 in 1974 . 53 in 1900 . 71 in 1950 . 83 in 1954
22 . 107 in 2001 . 53 in 1970 . 74 in 1961 . 80 in 1934
23 . 109 in 1936 . 55 in 1970 . 66 in 1947 . 79 in 2001
24 . 109 in 1981 . 58 in 1911 . 67 in 1947 . 80 in 2001
25 . 105 in 1964 . 58 in 1890 . 74 in 1904 . 83 in 1934
26 . 105 in 2006 . 57 in 2004 . 75 in 1996 . 79 in 1936
27 . 106 in 1986 . 58 in 2005 . 77 in 1911 . 80 in 1936
28 . 105 in 1980 . 56 in 2005 . 73 in 2004 . 79 in 1935
29 . 109 in 1978 . 55 in 1971 . 69 in 1971 . 80 in 1940
30 . 110 in 1986 . 54 in 1971 . 73 in 1903 . 78 in 1980
31 . 109 in 1934 . 53 in 1971 . 74 in 1962 . 79 in 1980