The weather in Makkah and Madinah tends to be dry with sharp temperature swings between day and night.
Drink water regularly even when not thirsty, at least two litres a day, and make use of zamzam water.
Wear a mask in crowds, particularly if you have a history of respiratory issues.
Do not force every voluntary act of worship when your body is tired. Prioritise the obligatory rites, then rest well.
Carry personal medication in your cabin bag along with a copy of the prescription, and inform the group medical officer of any medical history.