Given the proclamation he's just issued, either he's not sure himself, or he's desperately misinformed about what elected leaders are supposed to do in a crisis.
Pop quiz! When your state is in a long drought that's causing terrible fires and having bad effects on crops and livestock, what are appropriate responses a governor could undertake?
A: Declare a state of emergency
B: Redirect funds to additional firefighting equipment/personnel
C: Ask for help from the federal goverment
D: Issue an official proclamation declaring a three-day period as "Days of Prayer for Rain in the State of Texas"
If you answered some combination of A, B, and C (or other paths of material help that I didn't think of), pat yourself on the back! If you answered D, you're either Rick Perry, or just as deeply confused about appropriate uses of elected office.
Here's a hint for those who picked D: there is no appropriate place in the secular government of a highly diverse nation (or state) for proclamations, or declarations, or whatever the hell else, promoting religious practice. Prayer, in case you're still confused, is a religious practice. And even if you slip in the little "citizens of all faiths and traditions" line to try to make it less sectarian, you're still privileging belief over nonbelief. This is, for obvious reasons, Not Okay.
Is it too much to hope that I might see an end to government promotion of religiosity in this country, in my lifetime?
Look, I get the desperation of long drought and bad wildfires. I'm Californian born and raised. As I used to joke with friends from other parts of the country about the difference in seasons from one place to another, "Sure, California has seasons. Fire season and water season." I live in a state in which fireworks are mostly banned because of the regular fire danger during the summer. My family adopted a dog that had come to a rescue organization during the really nasty fire season in SoCal five years ago or so, when she quite literally just came trotting out of the burning areas alone as if her family had left her behind when they evacuated, who couldn't bark properly because of smoke inhalation. So I really, truly do understand the devastation a bad wildfire season and a bad drought can cause to a state. I sympathize with the people of Texas who are having to deal with this right now.
That does not change the fact that declarations urging people to pray for rain are not an appropriate response from a supposedly-secular government in a supposedly-secular country. People who are so inclined will pray for divine intervention in a time of crisis anyway. To use an elected position of power to tell everyone they should be praying and what they should be praying for is deeply inappropriate. Period.