During the winter the daytime air temperature usually varies from 65 to 75 degrees F.
From March to October, air temperature is usually from 70 to 90 degrees F.
Bring a hat and sun protection since the sun can be intense.
The wind season is from November to March, so take a sweatshirt or windbreaker for those cool and windy days
Nights are usually pretty cool especially during the winter. Take warm cloth with you.
Water temperature is around 70 degrees F during the winter, but because of the wind, a full wetsuit (3/2 or 4/3) is generally recommended. From March to November, a shorty is more than enough.
The best season for the wind is November to March when the wind usually blows daily from 11:00AM to 5:00PM at 15-20 knots.
ikitesurf.com has a realtime wind sensor available to its subscribers and offers a daily wind forecast during the winter season:
Realtime La Ventana wind sensor: http://www.ikitesurf.com/windandwhere.iws?regionID=130&siteID=1369
La Ventana wind forecast:
Check also the Buoyweather forecast