First we freeze then we bake.
A Nuclear Winter and a Nuclear Summers are just concepts, since no one really knows what will happen after a nuclear war but this is the hypothesis; after numerous nuclear bombs have exploded the world will be covered by flash-fires on a grand scale, which will deposit tons of ash (black carbon) into the air, darkening the sky, blocking much of the sun-light. All it will take is about 100 fire storms to burn at the same time for a small Nuclear Winter to begin. The effects of the ash will last for decades until rainfall (black rain) has washed it all away.
Finally, when you can see the light of the sun, Nuclear Summer begins, again just a concept. The green house effect takes over do to all the CO2 and methane gases from all the decomposing frozen bodies (plant and animal) that have thawed out after Nuclear Winter and has been pumped into the air.
Nothing will survive. Okay, okay, maybe one little germ or two or three bacteria but that's all.
*If you like my blogs check out my book "ONE TWO ONE TWO a ghost story, on sale at Amazon only $2.99 on Kindle or read it for free join Amazon Prime