In May, there was just 34% of the usual rainfall for the month
Last month was the warmest May in Scotland since records began in 1914, according to Met Office data.
The statistics showed May was also the fourth driest recorded, with just 34% of the usual rain for the month.
The climate updates revealed that January and February were both warmer than the long-term average.
Dr Richard Dixon, of WWF Scotland, said it was evidence that the climate was changing and called on governments to step up measures to tackle the problem.
He said: "Despite warnings that 2008 might be a cooler year than those we've experienced in recent times, May has smashed another temperature record.
"While enjoying some unexpected sun here in Scotland, we must not forget that climate change is hitting other parts of the world much harder than us.
"May also saw the devastating Cyclone Nargis hit Burma, with over 130,000 people killed or missing, and climate change is forecast to make storms worse around the world."
Dr Dixon, who is director of the charity in Scotland, also called for the planned rise in fuel duty not to be delayed.
"The response to those protesting for lower fuel prices should be co-ordinated long-term action to end our addiction to fossil fuels, not short-term price cuts that are good for neither businesses, people, nor the planet," he said.
"The Scottish Government is currently thinking about what to put in its Climate Change Bill.
"With 20,000 consultation responses from around the world they have had a strong message that people want this to be the world's best climate bill and for Scotland to set the benchmark for other developed countries."