i understand many bands have played this song, but this is the way the Tornadoes play it and
its my favorite recording of this song, if you havent heard it you oughta find a copy of it and
 have a listen
recorded 1964

"SUMMERTIME" as played by The Tornadoes
                                       (written 1935 by George Gershwin)

Dm (xx0231@1)           Bb (x1333x@1)               G (320003@1)              A|--------1------|------------------|----------------|---------------| (x02220@1)|------3----3---|---------3--------|----------------|--------2------|
|----2--------2-|------3-----3-----|--------0-------|------2---2----|
|--0------------|----3----------3--|-----0-----0----|----2-------2--|
|---------------|-1----------------|---2----------2-|-0-------------|
|---------------|------------------|-3--------------|---------------|

Dm (xx0231@1)       Bb (x1333x@1)name="chord_320003@1">G            A (x02220@1)      Dm (xx0231@1)     Bb (x1333x@1)  G (320003@1)   ASummertime, (x02220@1)    and the living is easy

Dm (xx0231@1)                       Afish (x02220@1)are jumping, and the cotton is high

A (x02220@1)          E (022100@1)          A|--------------------------------| (x02220@1)|--2-2-2-2-2-2----------------2--|
|--2-2-2-2-2-2---1-1-1-1-1-1--2--|
|--2-2-2-2-2-2---2-2-2-2-2-2--2--|
|--0-0-0-0-0-0---2-2-2-2-2-2--0--|
|----------------0-0-0-0-0-0-----|

Dm (xx0231@1) Bb (x1333x@1)   G (320003@1)        A (x02220@1)        Dm (xx0231@1)  Bb (x1333x@1)  G (320003@1)    AWell (x02220@1)your daddy's rich        and your momma's good looking

Dm (xx0231@1)        Bb (x1333x@1) G (320003@1) A (x02220@1)     Dm (xx0231@1)    Bb (x1333x@1)   G (320003@1)  Aso (x02220@1)hush little baby dont     you cry

music under sax solo does same Dm-Bb-G-A and ends with the A-E-A  riff.

rest of lyrics go:
One of these mornings
You're gonna to wake up crying
Then you'll spread your wings
And you'll take to the sky

But until that morning
There's a'nothing can harm you
With your daddy and mammy standing by

ends with Dm

and thats all! i hope this helps! i love this version and hopefully someone elso 
does and this is what 
they've been looking for their whole life. the Tornadoes lyrics are just a tad different.

-Bert