When Mr McDavitt began at MetService in the 1970s his forecasts gave the maximum temperature for the day and a tenuous prediction of the overnight low. In the 1980s, weather prediction was extended to the next day.
In 2012, MetService looks well into next week and makes millions of dollars selling weather reports to natural gas traders whose profits depend on the weather.
The senior meteorologist did not feel his role was threatened by "bedroom forecasters", such as the media-savvy weatherman Philip Duncan of Weatherwatch, who has muscled in on MetService's airtime.
"They're not in our area, and we're not in their area," he said. Besides, "We are scientists."
The meteorology seed was planted in his head at age 16 as he witnessed the storm which sank the Wahine in Wellington Harbour. He watched the wind knock over the chimney in the family house, which led to the roof catching on fire.
Remarked Mr McDavitt: "I really didn't have an appreciation of the weather until that point."
Studying mathematics and computer programming at Victoria University in the late 1960s, he became obsessed with chaos theory, or the pursuit of order in seemingly disordered things.
"I looked at the whole spectrum. You have astronomy which is patterned, and ordered ... to seismology and vulcanology which is very chaotic. And I wanted something in between, which is why I chose the weather."
Four decades of intense scrutiny of weather made him nearly certain of one chaotic pattern - the increase in extreme weather events, possibly because of a warming world.
The extreme event that stuck out in his memory was the first sight of Cyclone Bola evolving on his satellite map. He had the role of lead forecaster for the 1988 cyclone, which flooded parts of the North Island and killed three people.
He claimed he had no low points in his career, but felt a pang of guilt when a Canterbury farmer asked him for a clear day to cut his hay late in a rain-plagued season in 1983.
On his recommended day a shower ruined the farmer's crop, and he could not make his payments to the bank that year.
In retirement, Mr McDavitt will tear himself away from most satellite maps and weather instruments, but will act as a forecasting consultant for sailing groups and the like.
Always an intuitive forecaster, he said nearly everything you need to know about the weather can be learned with a quick glance at the sky.
"I will always be watching the clouds, every time I walk out the door."
Bob McDavitt
MetService weather ambassador
* Age: 59
* Meteorologist and forecaster for MetService in Wellington, Fiji, Christchurch, Auckland, 1975-2012
* Official forecaster for America's Cup campaigns in Perth and San Diego
* Team meteorologist for Barcelona Olympics, 1992
Memories
Most significant weather event: Cyclone Bola, 1988
Most overused phrase: "Weather is a mix of patterns and chaos."