The weather can play a key role in your chances of success at interview. Take the sunny spell we are currently experiencing. On the one hand good weather put's people in a positive frame of mind and therefore interviewers will subconsciously be more favourable towards candidates to do well. Candidates will also feel more positive. However if it is also hot then think ahead. Travel to an interview may be very hot and you have probably put your smartest clothes on which are probably not your coolest, so you will want to have time to cool down and 'dry out' before the interview. Not all companies enjoy air conditioning so if you find the interview room hot, ask to take your jacket off, although it is sometimes better to keep it on to cover up any obvious perspiration. Take a bottle of water and tray and stay hydrated. If you are in a group interview remember that everyone is in the same boat, although at risk of sounding sexist towards women and transsexuals, women's clothing can be a lot cooler than men's and so may have n unfair advantage.
Never the less I believe that good weather puts people in better moods and so on balance it helps rather than hinders
