Rainfall and climate
The Gu and Deyr rains, 1950 to 2023: every rainy season in numbers
Somalia's two rainy seasons, Gu (April to June) and Deyr (October to December), each bring about 125 mm of rain in an average year. The worst seasons since 1950 were the Deyr of 2010, at 11 percent of normal, the Deyr of 2021 (31 percent) and the Gu of 2022 (44 percent). Each was followed by severe hunger.
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Where these numbers come from
These figures are from ERA5, the climate reanalysis of the European Centre for Medium-Range Weather Forecasts. A reanalysis combines weather stations, satellites and a weather model to rebuild the rain for every month since 1950, even where there are no stations. We took Somalia's national monthly averages from the World Bank's Climate Change Knowledge Portal and added up the months of each season (World Bank Climate Change Knowledge Portal, ERA5; ECMWF, ERA5). "Normal" here means the 1991 to 2020 average. The full table for every year is in the data file somalia-gu-deyr-rainfall-1950-2023.csv on this page.
Why ERA5 and not station data. Somalia has had few working weather stations since 1991. The station-based CRU dataset, which the yearly rainfall page uses for the long view back to 1901, shows the Gu of 2022 as wet. ERA5 shows it as the driest Gu since 1950, which matches what farmers, herders and the World Meteorological Organization reported (WMO, August 2022). This site uses ERA5 for single seasons for that reason.
A normal year
Average rain by month, 1991 to 2020, ERA5 (same source):
- Jiilaal: January 6 mm, February 3 mm, March 12 mm
- Gu: April 64 mm, May 51 mm, June 8 mm. Season total about 123 mm.
- Xagaa: July 7 mm, August 7 mm, September 10 mm
- Deyr: October 58 mm, November 54 mm, December 17 mm. Season total about 130 mm.
The year totals about 297 mm, and the two seasons bring more than four fifths of it.
The driest seasons since 1950
Rain as a share of the normal season (same source):
- Deyr 2010: 11 percent. It was followed by a poor Gu in 2011 (84 percent). The UN declared famine in parts of southern Somalia in July 2011 (2011 East Africa drought, Wikipedia).
- Deyr 2021: 31 percent, then Gu 2022: 44 percent and Deyr 2022: 47 percent. Three failed seasons in a row, in the Horn of Africa's worst drought in more than 40 years (WMO, August 2022).
- Deyr 1974: 34 percent and Deyr 1975: 38 percent. This was the drought Somalis call Abaartii Dabadheer, "the long-tailed drought". The government declared a state of emergency in November 1974 (Hiiraan Online, 2014; Yeheb).
- Deyr 2016: 44 percent, followed by a below-normal Gu in 2017 (78 percent).
- Other dry Gu seasons: 1969 (59 percent), 1999 (61 percent), 1992 (68 percent), 2004 (68 percent) and 2014 (70 percent).
The wettest seasons
- Deyr 1997: 318 percent of normal, the wettest season in the record.
- Deyr 2023: 199 percent, in an El Niño year, straight after the long drought.
- Deyr 1951 (201 percent), Deyr 2004 (181 percent) and Deyr 2019 (181 percent).
- Gu 1953 (234 percent), Gu 1951 (213 percent) and Gu 2018 (166 percent).
What the record shows
- The Deyr swings more than the Gu. Since 1950 the Deyr has ranged from 11 to 318 percent of normal; the Gu from 44 to 234 percent.
- Bad Deyr seasons come before most hunger crises. The Deyr of 1974, 2010, 2016 and 2021 were each followed by a hard year. The Deyr rain feeds the pasture and water that herders depend on through the Jiilaal dry season, and the Gu harvest comes months later.
- Wet can follow dry. In 2023 the wettest Deyr since 1997 came straight after three seasons in a row with well below normal rain.
A national average hides big differences between regions. The farming regions between the Juba and Shabelle rivers depend most on the Gu harvest; the pastoral north depends on both seasons for pasture. For seasonal outlooks and hunger warnings by region, see FEWS NET and FSNAU (FEWS NET, Somalia; FAO FSNAU).
Related
Sources
- World Bank Climate Change Knowledge Portal, ERA5 · climateknowledgeportal.worldbank.org
- ECMWF, ERA5 · ecmwf.int
- WMO, August 2022 · wmo.int
- 2011 East Africa drought, Wikipedia · en.wikipedia.org
- Hiiraan Online, 2014 · hiiraan.com
- Yeheb · yeheb.org
- FEWS NET, Somalia · fews.net
- FAO FSNAU · fsnau.org
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Where this matters
- Beledweyne (Belet Weyne) and HiiraanHiiraan is a region of Hirshabelle State on the Shabelle river, with Beledweyne as its capital and about 505,000 to 598,000 people.
- Jowhar (Johar) and Middle ShabelleMiddle Shabelle is the farming region along the Shabelle river north of Mogadishu, with Jowhar as its capital and about 1 to 1.26 million people.
- Marka (Merca) and Lower ShabelleLower Shabelle is Somalia's biggest farming region, along the Shabelle river south-west of Mogadishu, with Marka (Merca) as its capital and about 835,000 to…
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- Xuddur (Hudur) and BakoolBakool is a region in South West State, on the border with Ethiopia, with Xudur (Hudur) as its capital.
- Garbahaarrey (Garbaharey) and GedoGedo is the south-western region on the borders with Kenya and Ethiopia, with Garbahaarrey as its capital and about 1 million people.
- Bu'aale (Buale) and Middle JubaMiddle Juba is a farming region on the Juba river in the south, with about 447,000 people.
- Kismaayo (Kismayo) and Lower JubaLower Juba is the far southern region on the border with Kenya, with the port city of Kismayo (Kismaayo) as its capital and about 1.2 million people.
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Keep reading
- Rainfall and temperature in Somalia since 1901: the climate in numbersSomalia's yearly rainfall and temperature from 1901 to 2023, the Gu and Deyr rainy seasons by month, the wettest and driest years, and the limits of the data.
- Rain by region in Somalia, 1991 to 2023: the Gu and Deyr in 18 townsGu and Deyr rainfall for the main town of each of Somalia's 18 regions, every year from 1991 to 2023, compared with normal, from ERA5 climate data.
- Temperature by region in Somalia, 1991 to 2023: 18 townsYearly average, hottest and coolest month, and highest and lowest temperatures for the main town of each of Somalia's 18 regions, 1991 to 2023, from NASA POWER data.