The northern French Alps are situated under the northeast corner of the Azores high pressure and have an excellent annual climate. There is good snow in winter, summer is hot with light winds and there is no excessive precipitation.
High alpine regions create their own weather patterns or micro-climates and weather blisters form over some areas sheltering them from outside influences and only powerful weather systems will infiltrate, causing complete but temporary changes. It's rare to encounter poor weather for more than a few days at a time!
As the majority of the flying is made in purely thermic conditions. The thermals are created by the warm sunshine and reasonable lapse rates and unlike dynamic flying conditions we are not waiting for the wind direction and strength to be just right before flying. In fact we are not concerned by the wind direction as all of our sites are for thermic flying. However in some areas close by afternoon dynamic or ridge flying forms where the terrain and wind direction allows.
Most of the year the meteo winds are light and the valley winds formed from rising thermic air blow most afternoons. Strong afternoon valley winds are only found in deep and narrow valleys when conditions are unstable. Wide open areas encounter much lighter afternoon valley wind conditions.
The mid winter flying window is around 2-3 hours extending to 11 hours in the spring and summer. Some mid summer days have strong thermic periods where pilots become grounded for a few hours, otherwise the annual flying conditions are very good. It has to be said that not all the days produce fantastic flying conditions but it's not bad here and better than many popular flying spots.
Below is a summary of the days flown each month from December to October during our working/flying months. As you can see the overall number doesn't change dramatically each year: the chart speaks for itself.
Please note the months that are marked n/a are months where there may have been flying but we were busy doing other activities. '*' marked months are show incomplete data due from time away from our local area.
December and January our prime skiing months are often stable, sunny, cloudless and cold. During this period thermals still form and the best flying is found between 11.00 - 1600hrs. The smooth thermals suit new pilots looking for gentle conditions.
By mid February lapse rates are improving and cumulus cloud starts to form over the high mountain peaks and cloud base can be reasonably high: 2000 - 2500m asl. Thermal climb rates can be 1-2m/s on the averager. (Variometer averager set at 15secs).
The general valley temperatures are down to -15°c at night and up to -4°c during the day. (some nights are colder and some days are warmer especially in the direct sunshine) Winds are mainly light apart from those arriving with weather fronts. Valley winds are very light!
In March and early April the sun now warms the lower snow free valleys allowing thermals to rise freely, and during the afternoon they are marked by cumulus cloud often rising to 2500 - 3000m asl. The flying window is longer: 11.00 - 17.00hrs. Thermal climb rates are better at 2-3 m/s.
The general valley temperatures are down to -8°c at night and up to +23°c. Depending upon the daily thermic conditions valley winds are becoming stronger especially in deep and narrow valleys where care is needed early to mid afternoon!
During April, May and June we enter some of the best thermic months. Cloud base reaches 3200 - 3500m asl, the atmosphere is generally unstable and the crisp thermals have good climb rates! Thermal climb rates average 4 m/s.
The flying window extends: 10.00 - 20.00hrs, though we occasionally experience strong lunchtime periods that ground most pilots but naturally coincide with the traditional French lunch period of 2-3 hours...
During these months we occasionally experience late afternoon or evening thunderstorms, though these are generally well forecasted beforehand.
The general valley temperatures are down to +5°c at night and up to +28°c in the day. Meteo winds are normally light, but beware of strong afternoon valley winds in deep and narrow valleys!
In July and to mid August the atmosphere is a little more humid and cloud base often only reaches 2500 - 3000m asl. However the days are warm if not hot and the flying day is long: 10.00 - 21.00hr.
In July evening thunderstorms are sometimes present, though generally so well forecasted we know when to expect them!
By August the strong lunchtime periods have subsided allowing air sports all through the day and thermal climbs rates still average 3-4 m/s but lessening as August arrives.
General valley temperatures are down to +15°c at night and up to +35°c in the day. Those strong valley winds are still present but they are starting to subside as autumn approaches!!
Late Summer - Autumn..
As Autumn approaches stable air returns and by September gentle thermals and friendly cumulus rise only to 2500 - 2800m asl. From mid August to October and into November the flying conditions mellow allowing good flying throughout the day.
October/November flying in the mountains is special. The golden autumn colours are glorious and the cool dry air has an incredible freshness about it! Thermal climb rates are 2-3 m/s and decreasing, and the best flying is found in the afternoon.
General valley temperatures are down to +7°c at night and up to +25°c in the day, though becoming cooler by late October. The valley winds are gentle and short lived.
Yes we do get rain and snow! It's cold here in winter and hot in summer but we have four beautiful and reliable seasons.
In winter and spring the cold fronts that pass usually only last 2-4 days and the snowline drops to 400m asl. By mid summer the snowline rises to around 3000m asl: there is always snow above this level as seen on the spectacular Mont Blanc (4810m) and surrounding high peaks.
In summer warm or occluded fronts bring just a little rain. These fronts rarely last for more than 2-3 days and any local thunderstorms are generally short lived often diminishing into a clear night.
As we live under high pressure our natural winds meteo winds come from the north and are nearly always light. All valley winds (anabatic winds) turn katabatic in the evening dropping away to nothing at night and when conditions allow we have superb restitution (magic lift/valley release/glass-off) flying in the evening.
So what does this all mean..
Beginners can join a course anytime from March to November. In spring and summer strong thermic breezes can halt flying for a few hours during the afternoon, though there is always extra ground training or interesting class room work available during these periods. Later in the year, mid August onwards it's possible to train and fly throughout the day without being challenged by the strong summer conditions.
Newly qualified pilots visiting the mountains will find smooth conditions up to April then after early August. However the mid summer days are long and missing 2 - 3 hours during the middle of the day is of little consequence as there is plenty of flying early and late in the day.
Aspiring thermal and cross country pilots should visit in the spring and mid summer months when the conditions are at their best!