I started late March last year and it was getting warm by late April. 28C by late afternoon.
Just be sensible. I'm sure you'll be fine.
It's possible to walk shorter days in many cases. Though walking the VdlP is a bit like a chess game, as you need to think a few moves / days ahead to plan your distances and likely stopping places.
I walked days that varied from 10 kms to 27 kms. The 27 kms (from Villafranca de los Barros to Torremejia) was hard to make any shorter, but it's not a hard day. Lovely walking track and dead flat! Just start very early to avoid the heat.
Take care to monitor your hydration levels. If you are not sure how to check just google it. Dehydration urine colour! Not drinking enough water is an easy trap to fall into. Leads to sore feet, joints etc.
Start well hydrated...before you start walking.
You will need a carry a fair bit of water. It is rare to be able to refill during the day unless you are passing through the larger villages/towns. Most days I carried 2 litres. on warm or longer days more. You'll soon get used to your water consumption. Mine is fairly constant at 10 kms / litre. But I need a bit more water above 30C.
Pre dawn starts are your friend! Most of the time you are on excellent tracks, and with a good headlamp, walking in the dark is easy. My routine start time became 30 mins before dawn. Hearing the animals and birds waking up and watching the dawn was truly amazing. I never appreciated why people started early. The main benefit of course, is that it's Cool! The hottest part of the day seemed to be 3-5 pm. So I aimed to finish by 2 pm. In time for a menu del dia!
It's worth reading about dawn v sun rise. Most weather apps will tell you the time of sun rise.
But dawn, is well before that, before the sun even appears.
You'll be able to walk with a head torch from about 60 minutes before sunrise for example. Or earlier if you like.
Starting an hour before sunrise, means you are only using your head torch for about 30 minutes.
I hope that makes sense.
Here's an example. Merida in May.
Calculations of sunrise and sunset in Mérida – Badajoz – Spain for May 2024. Generic astronomy calculator to calculate times for sunrise, sunset, moonrise, moonset for many cities, with daylight saving time and time zones taken in account.
Sunrise is at 7:27 am. But you might start well before that. As the sun comes up, the temperature starts to rise modestly till about 11 am, then it seems, more quickly to the peak part of the day.
Nautical Twilight as at 6:23 am. You can just make out the horizon.
Civil Twilight is at 6:58 am. It's plenty of light for walking without a head torch.
In this scenario, I would probably start walking at 6:15 am.
I might need my head torch for 30 minutes.
Of course you could start earlier, but then you are in the dark longer and missing the scenery.
But of course if the local bar opens for breakfast at 6:30 am, that throws out the whole thing!!
Your call.
The hottest part of the day is a bit counter intuitive.
In that link, you will see a reference to 'Solar Noon'. This is when the sun is at it's highest.
In this case it's 2:22 pm.
I seem to recall the hottest part of the day is a bit later than that (2 hours or so).
Maybe a Meteorologist will come along and explain why that is........
Lastly.......
I know that there is often debate about electrolytes and similar. But I think it's important to maintain salt levels in hot weather. Salty foods etc should suffice. But on the VdlP I actually took electrolyte tablets. (Salt Sticks). Hardly a scientific study, but I didn't suffer from energy loss and tired muscles as much as I used to.