You need to take a leave from your work of over one month for personal reasons. Write a letter to your boss. In your letter:

Dear Mr. Tyagi, I am Sfurna Patel, the senior executive of Designing Department of ongoing 'Southern Heights' project at California. I am writing this letter to request you to grant me a leave of one month that is from 22nd August to 23rd October. I need to take this leave for the following reasons. The primary reason for asking for leave is that my grandmother who resides in Toronto have to undergo heart surgery in upcoming days and it is suggested that she takes a complete bedrest for at least 20 days. Meanwhile someone is needed to attend her all time. As my grandmother is staying with my brother it would be more convenient if I stay there to look after her. As far as work is concerned, I have asked Junior Designer, Mr. Kumar, to keep me updated with structural and conceptual brief. I will scrutinize the design concepts thoroughly and revert with necessary changes. In addition, I have also worked out design strategy beforehand and had shared every details with team members. In my absence Mr. Kumar will be incharge of design apects and will manage to generate all required drawings. In case of any query I will be in contact through e-mail. I will be highly obliged if you understand my situation and give me positive response. Yours sincerely, Sfurna