Strasbourg, seat of the European Parliament and capital of Alsace, has a semi-continental climate, with cold winters and relatively warm summers. In fact, for its eastern position, the climate, more than "French", is "German", that is, that of the Rhine Valley, to which it belongs.
The average temperature of January is 1 °C (34 °F), that of July of 19.5 °C (67 °F). Here are the average temperatures.
Average temperatures - Strasbourg

Strasbourg	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Strasbourg	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	-2	-1	2	5	9	12	14	13	10	7	2	-1
Max (°C)	4	6	11	15	19	23	25	24	21	15	8	5
Min (°F)	28	30	36	41	48	54	57	55	50	45	36	30
Max (°F)	39	43	52	59	66	73	77	75	70	59	46	41

Precipitation amounts to 660 millimetres (26 inches) per year, so it's not plentiful, but it's well distributed over the seasons, because Atlantic depressions can pass all year round; however, the rains are more abundant between May and September, due to afternoon thunderstorms, which can erupt in the warm season.
Here is the average precipitation.
Average precipitation - Strasbourg

Strasbourg	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Strasbourg	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	35	35	45	45	80	70	75	60	65	60	45	50	665
Prec. (in)	1.4	1.4	1.8	1.8	3.1	2.8	3	2.4	2.6	2.4	1.8	2	26.2
Days	8	8	9	9	12	11	11	10	9	10	9	10	116

Winter, from December to February, is cold and gray, with average temperatures near freezing (0 °C or 32 °F). However, there are different weather situations: when currents come from the Atlantic Ocean, temperatures are fairly mild, so that highs can reach or exceed 10 °C (50 °F), it can rain and there can be a strong wind; when the atmosphere is more stable and the wind is weak, the temperatures are close to the average, and there can be fog and low clouds; but when cold winds blow from Eastern Europe, the temperature drops several degrees below freezing. For example, in February 2012 the temperature touched -15 °C (5 °F), in December 2010, -18 °C (0 °F), in February 1986 -20 °C (-4 °F), in January 1987 -19 °C (-2 °F), and in January 1985 -17 °C (1 °F), but way back in January 1942 it plunged to -24 °C (-11 °F).
Snowfalls are quite frequent, though generally not abundant.

Spring, from March to May, is cool, unstable and moderately rainy. The season is initially cold, with possible snow and frost in March, and then gradually becomes milder, but with some chance of cold periods still in April. In May, it can get cold, especially in the first half of the month, with lows close to freezing, but at other times the first warm days can occur, especially in the second half of the month, with the first afternoon thunderstorms.

In summer, from June to August, there are variable or sunny days, with pleasant temperatures, and some hot days, with highs equal to or above 30 °C (86 °F), and sometimes even up to 35/37 °C (95/99 °F). On sunny days, in the afternoon, thunderstorms can erupt. Sometimes there are also rainy and cool days. However, when Atlantic fronts pass, there can also be cool and rainy days.

Autumn, from September to November, is initially mild and not too rainy, and gradually becomes more gray, cold and rainy. In November, generally the first snowfalls and night frosts occur, but already in October it can sometimes be cold.



The amount of sunshine in Strasbourg is scarce in winter, when the days are usually dull and cloudy, while it is acceptable from May to August, when the sun shines for 7 hours per day on average.
Sunshine - Strasbourg

Strasbourg	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Strasbourg	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	2	3	4	6	7	7	7	7	5	3	2	1

The best time to visit Strasbourg goes from mid-May to late September. Some afternoon thunderstorms must be put into account, as well as some cool and rainy days, and even some hot days (especially from mid-June to mid-August), but generally the weather is pleasant.