Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (10.39 USD): bGhOnEy10
Coupon (10.55 USD): 13f142
(CouponsFromChina.com tip: you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): C1549, C1544, C15499, C15488, 4ee943, 502C6B, vipupgrade8, TTxBG10, aff7off, bgssaff9, AFfbG10, SKU851435, BGOWER4, BGC153, BGBFAFF2019, BGCITYADS2019, BGC159, 20%DG422
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Digoo DG-C15 Weather Forecast Station is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).