The climate in Alcalá de Henares is the continental Mediterranean, with cold, dry winters and hot, dry summers. The average year-round temperature is 14 °C (57 °F). The average year-round rainfall is about 420 mm (16.5 in), mainly in spring and autumn. Temperatures vary from some degrees below 0 °C (32 °F) in December and January to some over 40 °C (104 °F) in July and August. The dry season coincides with frequent heatwaves in summer.
Tabular view for temperature, days of rain and daylight hours per month
| Months | Temperature | Rain days | Daylight hours | ||
| Normal | Warmest | Coldest | |||
| January | 5 °C | 11 °C | 1 °C | 4.8 d | 9.7 h |
| February | 6 °C | 13 °C | 1 °C | 3.9 d | 10.7 h |
| March | 10 °C | 16 °C | 4 °C | 4.3 d | 12.0 h |
| April | 12 °C | 18 °C | 6 °C | 5.9 d | 13. h |
| May | 16 °C | 22 °C | 9 °C | 6.4 d | 14.5 h |
| June | 22 °C | 29 °C | 14 °C | 4.0 d | 15.0 h |
| July | 25 °C | 33 °C | 17 °C | 1.8 d | 14.7 h |
| August | 25 °C | 32 °C | 16 °C | 2.1 d | 13.7 h |
| September | 20 °C | 27 °C | 13 °C | 3.4 d | 12.4 h |
| October | 14 °C | 20 °C | 9 °C | 6.1 d | 11.1 h |
| November | 9 °C | 14 °C | 4 °C | 5.8 d | 9.9 h |
| December | 6 °C | 11 °C | 2 °C | 5,0 d | 9,3 h |
During May, the temperature is around 22º C.
