For people who appreciate four seasons but prefer a longer summer, DC has an ideal climate. Spring and fall are mild and pleasant with moderate temperatures and little humidity. The warmer season begins sometimes as early as March and can last into November. However, summer humidity can be stifling, and winter cold includes an occasional blizzard. The variety of plant life brought to the capital from all over the world provides beautiful springtime blooms but horrendous seasonal pollen. Allergy sufferers beware! Average temperatures in the winter range from 30 to 40°F; the average summer high temperature is 95°F. Most buildings have intense air conditioning systems. Umbrellas are useful year round.