Average monthly and annual values in Stuttgart


July




July is the summer month with the highest temperatures. The concentration of most pollutants is on a minimum level. This is partly due to a practically non-existing heating activity.

Strong insolation with values up to 1,000 W/m² in our region initiate, however, a chemical reaction of the air which leads to increased ozone creation. What contributes to ozone creation are nitrogen oxides and hydrocarbons, substances mainly caused by the traffic sector. This is why ozone levels are very high in July, especially during a high-pressure weather situation and when wind speeds are relatively low. So we see that periods of clear weather are not merely positive in summer!

When the ambient air concentration of ozone exceeds the critical value of 180 µg/m³, the Environment Ministry informs the population via the media. Further information can be found on BTX or teletext (Saarländischer Rundfunk SR 3, page 164). The generally low level of air pollution in July is also the consequence of an intensive, vertical mixing of the air and the resulting rarefaction of air pollutants in the atmosphere.

The high position of the sun in July brings about the constant warming of North Sea, Baltic Sea and North Atlantic and thus increasing air temperatures until the middle of the month. This is the height of summer. So July is the hottest month of the year with an average temperature of 65.8 °F (18.8 °C) in the inner city and 63.3 °F (17.4 °C) in the higher district of Hohenheim. Cells of the Azores high can now detach and come to Europe. Heat waves occur but they do not last for long and are interrupted by cooler periods. The consequence is a maximum amount of thunderstorms. The highest temperature recorded was 98.9 °F (37.2 °C) in Stuttgart. July has also the biggest amount of sunshine hours of the year with an average of 233 hours.

Weather lore:

- St. Swithin's Day (15 July), if thou dost rain, for forty days it will remain.

- When it rains on St. Swithin's Day, it is the Saint christening the apples.

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Average monthly values of the climatic elements measured in Stuttgart-Zentrum (312 m), Stuttgart-Schnarrenberg (314) and Stuttgart-Hohenheim (420 m)

 

Climatic element	STUTTGART		Stuttgart-Hohenheim
	Stadtmitte 1951-1980	Schnarrenberg 1961-1990**	1951-1980	1961-1990
Average temperature (in °F/°C)	65.8/ 18.8	65.1/ 18.4	63.3/ 17.4	64.0/ 17.8
Maximum temperature (in °F/°C)	98.9/ 37.2 (1984)	98.2/ 36.8	97.5/ 36.4 (1984)	-
Minimum temperature (in °F/°C)	41.0/ 5.0 (1962)	40.1/ 4.5	38.5/ 3.6 (1962)	-
Ice days (in days)	0	0	0	0
Frost days (in days)	0	0	0	0
Heating days (in days)	4.7	-	8.7	-
Degree-day figure *	18	-	-	-
Summer days (in days)	11.6	11	9.5	10.2
Hot days (in days)	2.9	-	1.8	2.0
Sultry days (in days)	5.8	-	-	-
Rain days (in days)	12.7	12	14.3	13.8
Thunderstorm days (in days)	-	-	5.1	5.9
Amount of precipitation (in mm)	69	63	71	72
Evaporation (in mm)	-	70	-	-
Highes point of the sun (degrees)	63	63	63	63
Possible sunshine hours (in hours)	481	481	481	481
Average amount of sunshine hours (in hours)	233	-	233	237
Global radiation (in W/m²)	-	-	237	-

 

(Figures in red respresent the years between 1961-1990, figures in black the years between 1951-1980)
*( degree-day figure = average from the years 1982 - 1997)
**( after the relocation of the Weather Central, the given values are those for Stuttgart - Schnarrenberg)

 

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© City of Stuttgart, Office for Environmental Protection, Section of Urban Climatology

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