Suggestions before you pack your suitcase
You will be traveling to Algarve, the southern part of Portugal in July.
Weather in the Iberian Peninsula is usually hot at this part of the year, so get ready for high temperature.
Keep in mind maximum average temperature in this area in July is around 30 degrees celsius, minimal average is ~20. From 12h to 16h is usually the hotter part of the day, but we may hit ~33-35 degrees celsius by that time if you stay at sun. Morning and evening are usually fresher, between 20-25 degrees celsius, so you may need put something on you if you are sensitive to cold. But probably that is summer for you in your country of origin ;-).
We suggest you pack light your suitcase with short pants and t-shirts / shirts. Some thin sweatshirt to put on you just in case we get some late evening fresh wind from the ocean. Caps and sunglasses are also very convenient. People that are more sensible to sunburn should bring sun protection with them, but you can usually find them in local supermarkets at your arrival too, of course. Take a bottle of water with you that you can refill, tap water is drinkable, no issue.
You may also want to take a towel and swimsuit, in case you decide to join us on Friday evening to the beach.
Just in case of any doubt, rain is very much unlikely at this part of the year :-).