In high latitude winters, snow provides light and contrast - without it the world is just shades of black brown grey. Some people there may think a little extra warmth could be welcome, but -2ºC with snow is much better than +2ºC with cold grey drizzle.
Your first sentence is correct. But if you look at the historical data, the sharpest drop in chinese fertility rate was several years before they introduced the one-child policy, which also ended several years ago without apparently making any difference. Also, fertility rates in Taiwan, South Korea, Japan are even lower. As these rates are also lower than europe, that maybe related more to housing affordability and density, possibly combined with some common evolution of ‘eastern’ values.