Actually the average days travel for wagon trains was 10 miles a day...
and that was with oxen which were stronger and more durable than horses...
These people stoppesd along the way too...
They would stay at a place they called Winter Quarters...
Did Brigham Young provide for the families there ???
Often the mormons had to beg from the symathetic non-mormons along the trail...
APOSTATES ???? Oh noes...
many mormons almost starved to death at Winter Quarters...
and some usually died...
Brigham Young could have cared less...
He needed warm bodies ...
Men to build up his army of vigilantes..
Women to be the extra “wives” he had promised the men as an allure...
and slaves to work in his kingdom...
So the families may have been left in July but probably struggled for over a year before the men folk came back.
I am pretty sure there is winter in the year.