For a walk from Almeria to Cordoba from 3/May to 22/May, you're likely to encounter the highest temperatures toward the end of your walk in Cordoba, since Cordoba gets hotter than other places on the route as summer approaches. So lets look at Cordoba to start:
In Córdoba during May average daily high temperatures increase from 75°F to 85°F and the fraction of time spent overcast or mostly cloudy decreases from 39% to 31%.
weatherspark.com
Click on the month of May to drill down to the detail. Around 21/May, it shows:
Average daily high temp. = 27℃ (max. historical temp. is around 33℃)
Average daily low temp. = 13℃ (min. historical temp. is around 10℃)
You can click further to see what that looks like over the course of the day.
On an average 22/May, you'll be feeling cool (14℃) at 7:15 AM when the sun comes up. The temperature will rise through the day. From 2pm to 8pm it will be over 25℃ with a peak of 27℃ at about 5pm
If you are unfortunate enough to experience something like the hottest recorded temperatures for that date, the temperature will be 18℃ at daybreak. From around 2pm to 9pm it will be above 30℃, with a peak of about 33℃ at about 5pm.
Bottom line - If the forecast is for record breaking heat, you should plan on setting off before dawn and covering as much distance as possible before 2pm.