Hello Zakkiya! I have made some corrections and alterations in your writing. There were a few points where I was unclear as to what you had intended to say, so I wrote comments in brackets. Some of your own words are in square brackets, and my comments are in regular brackets. My intention was that you could see why certain corrections were made. I hope that makes it clear for you, and that you find it helpful!
Trudging home one humid afternoon with my whining younger sister, after an uneventful and seemingly everlasting day at school, I could feel the grey atmosphere becoming [unusually choppy]. (What do you mean to convey by ‘choppy atmosphere’?)
The relentless wind was howling around us like a pack of ravenous wolves. A strong odour of dust hung in the sticky air which [seemed] as thick as soup. (You have already used the word ‘seem’ in your previous sentence in the form ‘seemingly’. Consider replacing it with a more sensory word… play around with how you might feel air. It could be simply the sticky air ‘felt’ or maybe you can taste the dusty air that is thick as soup.)
''I'm hot!'' moaned my [annoying] sister as she carelessly unzipped her [luminous] pink jacket and flung it off her shoulders. (Consider removing annoying, as it is implied by the moaning. ‘Luminous’ is a bit out of context with a jacket, as it would be used to describe something that emits its own light. Although fluorescent may work better, seeing as it is used to describe both light and colour.)
I walked on, ignoring her as she slowly trailed behind. (You started the sentence with the present participle ‘ignoring’ and finished it with ‘letting’. Particularly in such a short sentence, you should avoid doing that, because it sounds awkward. Rewording the sentence a little bit makes it less confusing as to which actions are happening at a given moment.)
[All of a sudden, and with no warning] the heavens opened up, and shed thousands of tears onto the muddy ground. (Choose one or the other, but not both. Your next sentence identifies this as a ‘deafening’ storm, but your context is not set up in this sentence. Try to introduce some sense of noise or power in this sentence, by perhaps using an adverb with ‘shed’ or adjective with ‘tears’.)
The deafening sounds of the raging storm were tremendous. Glancing up the ghostly and deserted street, I noticed, with a stab of lonesome fear, that my sister and I were alone.
''Hey! I'm drenched! Where's everyone disappeared to?'' hollered my sister. I [glanced] back and saw the terror in her wide eyes. (You have already used ‘glance’ in your previous sentence. Find a synonym. Removed open. That is obvious in the context)
''Don't worry!'' I comforted her. “Here's somewhere we can take shelter until this storm calms down!''
Diving hastily behind a reeking bright yellow bin, I dragged her in after me. She was shivering out of cold and fear, and her dark auburn hair was soaked to the roots.
Pulling my sister close to me for warmth, I peered out from our shelter. The dark sky looked like black ink spilled from a bottle and the sheets of rain were cascading down in colossal torrents.
How I wished I was in the safety of our cozy home, drinking a steaming mug of hot chocolate and watching the angry storm with curiosity from my large bedroom windows.
An earsplitting rumbling in the distance brought me out of my longing, and after a moment flashes of lightning ripped through the sky like a stabbing knife. (It is better to write either ‘longing’ or something like ‘drifting thoughts’, because ‘longing’ and ‘thoughts’ are very close in substance.) Shrinking back into our temporary hiding place, I wondered dismally how long this fierce storm would last.
(One last note: have you considered giving your sister a name? This would useful to mix into your text, seeing as you have much repetition of ‘my sister’. It would be more fluid if you could interchange ‘my sister’, ‘she’ and a name.) Hope this helps! : D
I forgot to mention:
You wrote 'an earsplitting rumbling'. Change this to 'an earsplitting rumble'.
After reading my correction on 'longing' again, I would replace it with 'reverie'.
I feel like it would fit your intention perfectly, and it sounds nice :)
Using 'refuge' instead of 'hiding place' would work well: 'temporary refuge'.
Okay, that's all, finally!
Thank you Lital, for all your comments and help. I will try and implement your advise in my future writings
isn't the question actually something like "You're walking home alone when you....." ??