Almost all of Portugal was in severe drought at the end of May, the country’s weather service (IPMA) said on Thursday.
Last month was the hottest May on record in the country since 1931, the IPMA said in its monthly climate report.
The average temperature (19°C) was more than 3°C higher than usual, it added. It makes it the hottest May on record in 92 years.
At the same time, the average rainfall of just under 9 millimetres was just 13 per cent of what would normally be expected.
As a result, the IPMA noted a "very significant increase" in the number of areas under "severe drought", which now covers 97 per cent of Portugal. This is just one classification lower than the weather service’s worst category of “extreme drought.”
Some of the country, 1.4 per cent, did fall into this extreme category and the remaining 1.5 per cent has been classified as being in "moderate drought".
It is a sharp increase from the previous month when drought impacted just 4.3 per cent of the country. During April, nowhere in the country was suffering from "extreme drought" either.
Is climate change to blame for Portugal's severe drought?
This year, Portugal has already seen the fourth hottest and fifth driest winter since records began in 1931. In February, rainfall was at just 7 per cent of the country's 30 year average for this time of year.
The government began restricting the use of reservoirs for hydroelectric power to save supplies for homes and farming.
"This deficit in rainfall that we are observing is in line with the trend of the last 20 years, marked by more frequent dry periods as a result of climate change," Vanda Pires, a climatologist from the IPMA, told AFP.
Climate scientists say the country can expect higher temperatures and lower rainfall as a consequence of global warming. They anticipate that heatwaves will become more common, last for longer and be more intense.
From Friday, Portugal could see "a sharp rise in temperatures, which may reach 40 degrees celsius," Pires said.
As a result, a warning has been issued for an increased risk of wildfires with authorities mobilizing around 5,000 staff this weekend.