With the arrival of hot summer days, the frequency of watering increases. Not only hot sun but also hot wind drues out the pots very quickly.
Things that dictate the amount of watering:
Position of your plant, and size of your pot. The smaller and shallower the pot, the more frequently watering is required. It is imperative to protect your plants from the hot afternoon sun and winds.
The soil mixture that you are using will determine how much watering your bonsai will need.
Put under your pot a wet piece of carpet, newspaper, or a tray full of gravel and keep that moist. This will increase the humidity and keep your pots from overheating.
Every time you are watering, make sure water drains from the holes at the bottom of your pot. This is what keeps the carpet or newspaper moist. With your watering, not only do you need to dissolve minerals for the roots and keep the roots moist and cool, this also brings fresh air to the roots.
Cover your pot (not tree) with a towel to prevent over heating of the roots and soil throughout summer, especially on days that reach 35-40 degrees celcius. Cut the towel to a size that will hang over the sides of the pot. cut a hole in the centre of the towel and then slipover the tree to lie on top of the soil. Keep watering up as normal.
Trim the burnt leaves off your tree to encourage growth.