Depends on the exact symptoms, artemis_mo. If you have noticed that the leaves are turning yellow all over, including the leaf veins, then yes, I would suggest moving the plant so it gets shade starting earlier than 12:30pm. Those are the symptoms of sunscald. But, if you are seeing browning of the leaves, that suggests moisture issues very likely caused by the high temperatures. Moving the plant because the leaves are browning would not help resolve the problem; a new location might provide shade earlier but the plant would still have to deal with the same high temperatures and reduced humidity during the summer. And those are (some of) the causes of browning of the leaves. So choose how to proceed based on whether the plant leaves are yellowing or browning.

Hydrangeas where I live need shade starting at 11am; otherwise the leaves turn yellow (or white in other places, as if bleached by the sun). I had this happen once when the tree that provided shade to one hydrangea was damaged by hail. When this happened, I left the yellowing leaves out there since only leaves in direct contatct with the sun are affected. Had I removed these, the the next set of leaves would have yellowed out. This gave me time to come up with a temporary fix. Now, starting in mid-July, the temperatures here hit highs around 100-115 daily until September. As a result, we get some browning of leaves due to lack of moisture.

Lack of moisture can be addressed by making sure that you have lots of (any type of) acidic mulch up to the drip line or beyond. About 3-4" of mulch will help maintain the soil underneath moist while the top of the mulch remains dry looking. I also try to water slowly and deeply with drip irrigation when the soil feels almost dry to the touch at a depth of 4".

Wilting can also be caused by windy location so if you shrub is in a windy location, do consider transplanting it. If you have to transplant, I would do it later. I have a camellia awaiting transplant right now because it gets too much sun and the leaves were showing signs of sunscald. In the meantime, it is receiving shade from one of those umbrellas you use in patios to provide shade around small round tables. It was going to be thrown away but I decided to keep it for this type of emergency.

Luis

Thanks Luis. I think my poor Annie is in trouble! There aren't many leaves left and most are totally wilted, but still green, and the rest are brown and crispy. I live in Missouri and today it was 100 degrees with 80% humidity. Heat index was 110 and there was plenty of wind and it is quite often windy and hot. So I guess it is a combination of all the factors you mentioned: sun, heat, wind and moisture. For now I will make sure she gets watered properly and check the soil daily.
When do you suggest I move her? What would be considered an ideal location?
Thanks for your time.

Since there is no sign of sunscald on the plant, you get to choose when. If you move it "now", be sure you have the time needed to check it often. If you are too busy now to do that then continue monitoring it but transplant it later.

As I mentioned earlier, I have a camellia soon to be transplanted to a shadier loccation. A newly purchased camellia still in a pot and a rose also in a container. Too hot out there to be digging so they will have to wait until fall when the temperatures are cooler.

An ideal location here provides part shade around lunch time, has soil that drains well, is mulched (3-4"), is not windy and allows the plant to grow to its mature height/width. As you move up north, some of that changes and you are allowed more sun (> 4 hours per day).

Your Annie is not the only one wilting. Our temps here are in the 105s so all my hydrangeas wilted and joined the club.

Try to view wilting as a nice defense mechanism that the plant uses and understand that your goal is not supposed to be to stop wilting "above all else". Your goal is to help the plant if you notice extreme wilting. After all, if you try to stop wilting so the plant leaves looks nice all the time, you end up watering every day, watering all afternoons and then the plant gets root rot and dies. :o((

Arborescens are tough plants so mulch, mulch, mulch; check the soil moisture by hand and water if it starts to dry out; and of course, (1) water immediately if the wilting episode is extreme or (2) water if the wilting episode is not extreme but the shrub is still wilted by next morning.

Luis

I think Annabelle should move.Master Gardener Paul James said, "I've seen hydrangea's wilt even from the early morning sun" I too have Annabelle. She gets shade until late in the day and then its screaming hot sun,(Yes even in zone 4 bordering on zone 3) and I'm still having trouble with annabelle!
I think water is important but even more so is shade,especially for annabelle. I have a limelight and it can withstand more sun,in fact I prefer 'Limelight' to 'Annabelle', but I won't tell her that!!!!!!!
Good Luck

Thanks. I will move her today to a shady location. Now I must decide what to put in her vacated spot. I want another hydrangea. Any suggestions? This spot gets sun until around 12:30, then shade. Lady In Red sits nearby and does fine with this amount of sun/shade, however she did not bloom this year. It is her 2nd year. Maybe not enough sun? Pink Diamond is also close by and doing well.