I've written the following code to process files within 2 separate folders, 'Daily Max 2015' and 'Daily Min 2015'. The workspace is set to: "C:\Users\uma.bhandaram\Desktop\DailyMax2015\Shapefiles". With this, the code works.

import arcpy
import os
from arcpy import env
from arcpy.sa import *

#Set workspace to Max Temps folder and allow for overwrite
env.overwriteOutput = True
env.workspace = "C:\Users\uma.bhandaram\Desktop\DailyMax2015\Shapefiles"

#Get Max Temp shapefiles and convert them to Raster
shpFileList = arcpy.ListFiles("*.shp")
for shpFile in shpFileList:
    # geoprocessing steps
    shpFileName = os.path.splitext (shpFile)[0]
    rastFile = shpFileName + ".tif"
    arcpy.PointToRaster_conversion(shpFile, "Max_2015", rastFile, "MOST_FREQUENT", "", 0.05)

    #Get raster files and run through Raster Calculator to see if Max  threshold has been met
    rastFileList = arcpy.ListFiles("*.tif")
    for rastFile in rastFileList:
        #geoprocessing steps
        rastFileName = os.path.splitext (rastFile) [0]
        MaxRstIn = Raster(rastFile)
        MaxRstOut = Con(MaxRstIn, 1, 0, "VALUE <=85")
        MaxRstOut.save("Con" + rastFile)

 #Set workspace to Min Temps folder and allow overwrite 
 env.overwriteOutput = True
 env.workspace = "C:\Users\uma.bhandaram\Desktop\DailyMin2015"

 #Loop through Min Temp shapefiles and convert them to Raster
 shpFileList = arcpy.ListFiles("*.shp")
 for shpFile in shpFileList:
    shpFileName = os.path.splitext (shpFile)[0]
    rastFile = shpFileName + ".tif"
    arcpy.PointToRaster_conversion(shpFile, "Min_2015", rastFile, "MOST_FREQUENT", "", 0.05)

    #Loop through raster files and run through Raster Calculator to see if Min threshold has been met
    rastFileList = arcpy.ListFiles("*.tif")
    for rastFile in rastFileList:
        rastFileName = os.path.splitext (rastFile) [0]
        MinRstIn = Raster(rastFile)
        MinRstOut = Con(MinRstIn, 1, 0, "VALUE >=45")
        MinRstOut.save("Con" + rastFile)

I need to find the sum of the each corresponding Daily Max and Daily Min file so I brought them together in a '2015' file and run Cell Statistics. Accordingly, I changed the workspace to: "C:\Users\uma.bhandaram\Desktop\2015\DailyMax2015\Shapefiles"

import arcpy
import os
from arcpy import env
from arcpy.sa import *

#Set workspace to Max Temps folder and allow for overwrite
env.overwriteOutput = True
env.workspace = "C:\Users\uma.bhandaram\Desktop\2015\DailyMax2015\Shapefiles"

#Get Max Temp shapefiles and convert them to Raster
shpFileList = arcpy.ListFiles("*.shp")
for shpFile in shpFileList:
    # geoprocessing steps
    shpFileName = os.path.splitext (shpFile)[0]
    rastFile = shpFileName + ".tif"
    arcpy.PointToRaster_conversion(shpFile, "Max_2015", rastFile, "MOST_FREQUENT", "", 0.05)

    #Get raster files and run through Raster Calculator to see if Max  threshold has been met
    rastFileList = arcpy.ListFiles("*.tif")
    for rastFile in rastFileList:
        #geoprocessing steps
        rastFileName = os.path.splitext (rastFile) [0]
        MaxRstIn = Raster(rastFile)
        MaxRstOut = Con(MaxRstIn, 1, 0, "VALUE <=85")
        MaxRstOut.save("Con" + rastFile)

 #Set workspace to Min Temps folder and allow overwrite 
 env.overwriteOutput = True
 env.workspace = "C:\Users\uma.bhandaram\Desktop\2015\DailyMin2015"

 #Loop through Min Temp shapefiles and convert them to Raster
 shpFileList = arcpy.ListFiles("*.shp")
 for shpFile in shpFileList:
    shpFileName = os.path.splitext (shpFile)[0]
    rastFile = shpFileName + ".tif"
    arcpy.PointToRaster_conversion(shpFile, "Min_2015", rastFile, "MOST_FREQUENT", "", 0.05)

    #Loop through raster files and run through Raster Calculator to see if Min threshold has been met
    rastFileList = arcpy.ListFiles("*.tif")
    for rastFile in rastFileList:
        rastFileName = os.path.splitext (rastFile) [0]
        MinRstIn = Raster(rastFile)
        MinRstOut = Con(MinRstIn, 1, 0, "VALUE >=45")
        MinRstOut.save("Con" + rastFile)

But, with this one change, I get the following error: Traceback (most recent call last): File "C:\Users\uma.bhandaram\Desktop\Python\Script3.py", line 12, in for shpFile in shpFileList: TypeError: 'NoneType' object is not iterable

The data are there - any thoughts on why this error? I'm working with Python 2.7 and ArcGIS 10.3

Much thanks.