I pulled some data regarding your ET just to verify that the algorithms are generating similar last year/this year.
You’ll notice similar ET data, but one is from July of last year. The main factor that is affecting the difference here is windspeed.
Raw ET 0.309
Date 2017-05-29
Max Temp 78
Min Temp 51
Station KHIF
Humidity avg 0.37
Windspeed avg 12.3
Dewpoint avg 37.04
Cloud cover avg 0
Raw ET 0.307
Date 2016-07-01
Max Temp 85
Min Temp 64
Station KHIF
Humidity avg 0.43
Windspeed avg 8.89
Dewpoint avg 49.82
Cloud cover avg 0.1
@azdavidr Here is some of your data, just as high ET last year 
Raw ET 0.4
Date 2017-06-03
Max Temp 105
Min Temp 78
Station KPHX
Humidity avg 0.15
Windspeed avg 7.21
Dewpoint avg 37.22
Cloud cover avg 0.34
Raw ET 0.39
Date 2016-06-11
Max Temp 100
Min Temp 80
Station KPHX
Humidity avg 0.34
Windspeed avg 10.07
Dewpoint avg 57.56
Cloud cover avg 0.43
I also reviewed the ET calculator code and it has not changed.
@runner1717 @dblagent007 @azdavidr @Modawg2k
I would adjust your crop coefficient down (less frequency, no change in duration) if you want to water less days.
