What Temperature Can Fleas Survive In The Winter?

Fleas can survive temperatures of above 49 degrees F. Adult fleas will often die when exposed to cold temperatures below 49 degrees F. If they are sheltered though, the cold weather will not kill the fleas. Fleas that are in the cocoon or pupa and larva stage are able to survive winter. Cold weather will not really be a dependable flea control.
Fleas are definitely pests. The tiny insect will cause pets and people and any other animal to scratch and itch and on occasion get sick. A flea is a wingless, small, blood-feeding insect that usually infests domestic cats and dogs and other pets. They can infect people and animals with diseases and parasites, and jump exceedingly far. A flea feeds off blood of animals and birds. They are quite difficult to kill and have a pretty tough body. Did you know that a flea is capable of biting your pet over 400 times every day?
Fleas will be most active during autumn and spring. A flea thrives in a humid climate with temperatures of up to 80 F. An adult flea will usually die during freezing temperatures. The immature offspring will lie dormant until the temperature warms up. A flea can survive throughout the year inside your home when it is protected from the extreme temperatures.
There are more than 2,000 known flea species. A normal flea has four stages of life. The adult flea will lay about 50 eggs each day. Eggs will drop into pet hair, soil, bedding or carpets. The egg will hatch within two days or several weeks. A larva will emerge and about two weeks later will spin in to a cocoon. It will now be a pupa. It stays like this for sometimes up to a year until the conditions are ideal.

Using dehumidifiers with air conditioning and vacuuming all may interrupt the flea life cycle.
Humidity is critical to flea survival. Eggs need relative humidity of
at least 70–75% to hatch, and larvae need at least 50% humidity to
survive. In humid areas, about 20% of the eggs survive to adulthood; in arid areas, less than 5% complete the cycle.^[19] Fleas thrive at higher temperatures, but need 70° to 90°F (21° to 32°C)
to survive. Lower temperatures slow down or completely interrupt the
flea life-cycle. A laboratory study done at the University of California
showed that vacuuming catches about 96% of adult fleas but the vacuum bag must be disposed of immediately afterwards. A combination
of controlled humidity, temperature, and vacuuming should eliminate
fleas from an environment, and altering even one of these environmental
factors may be enough to drastically lower and eliminate an infestation.

Fleas are small insects from the order Siphonaptera. They act as external parasites and live on blood of mammals and birds.  There is no specific temperature range that can make survival difficult for fleas in winter. Normally they live through winter, however a temperature below freezing point can limit their lives. For more information see the link below:
en.wikipedia.org

I'm not sure but I will tell you that I have 2 cats and usually over the summer the exact same time every ( may to sept) we have this flea problem. It's embarrassing to have company and your scared to ride with friends hoping that you don't take one with you and infest thier car, but it is now feb and ive gptten bit by 3 fleas this month which tells me that they are still alive somewhere. My guess would be in the carpet since that's obviously one of thier favorite spot

I cannot understand how a flea can survive in cold weather. If most insects pass out in temperatures around 40-50 degrees, then how can a flea survive any better than a cockroach? Please explain the possibility how it can survive hypothermia.