The phrase "abnormally cold" is correct and usable in written English.
It can be used to describe temperatures that are significantly lower than what is considered normal for a particular time or place.
Example: "This winter has been abnormally cold, with temperatures dropping well below freezing for weeks on end."
Alternatives: "unusually cold" or "exceptionally cold".
It periodically alternates with an abnormally cold stretch of equatorial water, sometimes called La Nina.
Last year, abnormally cold weather caused a substantial percentage of the blossoms to turn brown.
By Saturday, abnormally cold weather will extend from Bismarck to Baltimore.
It's growing faster than it was earlier this year, when the abnormally cold weather had a real impact.
While abnormally cold conditions have gripped Eurasia, temperatures have soared to their highest levels on record in the Arctic for the time of year.
After last year's polar vortex disruption in February, abnormally cold and stormy weather dominated the eastern U.S. in March and well into April.
A sequence of what appear to be abnormally long cold winters meant the trees grew slowly and steadily.
As time passes, he realizes the system is heading towards Chicago, joined by an unusual warm storm coming from the south, which is already causing a record-breaking heat wave in the city, and an abnormally early cold front from the Arctic.
Sure they wrapped in January and February statistics which were abnormally low due to extreme cold.
Note that the US is experiencing both abnormally warm (red-orange) and cold (green to purple) weather simultaneously.
This 5% chance of a mistake arises from unavoidable randomness, such as the normal variation in disease duration and severity; in the case of the echinacea studies you might just happen to test your drug on a group of people who happened to get lucky and got colds which were abnormally weak.
