There is a new Temperature tool available, which lets you interrogate any US temperature station from the 1,218 official NOAA climatology stations. Here is the link for the 1970 Max Temps for San Antonio ...
Graphing Remember that the the late 1970s was the time of our recent little ice age scare, when it snowed in Miami in 1977. You can even see that cold dip in the San Antonio graph, but just clicking on the "Reset Zoom" at the top.