This annual plant is classified as a warm-season crop. Temperatures even a few degrees above freezing may cause serious damage to both plant and fruit.
The optimum temperature for growth, yield and fruit quality of tomatoes is an average daily mean of 20°C to 24°C.
At temperatures below 12°C or above 35°C, flowers are often shed, with a consequent poor fruit set; the quality of the fruits produced under such conditions may also be detrimentally affected.
Even in frost-free areas, winter production of tomatoes should not be attempted where mean temperatures frequently drop below the critical margin of 12°C.
The best soil temperature for germination of tomato seed is from 15°C to 30°C. At such temperatures plant emergence occurs in about 7 to 10 days.
At temperatures of only 10°C this period may extend to three weeks or longer, and emergence tends to be more uneven and poorer.
The germination capacity is detrimentally affected at soil temperatures of over 35°C.
Hot, dry winds may cause an excessive flower-drop, even when soils are moist. Strong winds can cause serious mechanical damage.
Continuous moist, rainy weather promotes the occurrence and spread of leaf diseases, and also makes their control more difficult.
For best results, tomatoes should be grown in relatively dry areas under irrigation.
India-
Tomato prefers moderate temperature and thrives well in the temperature range of 25 – 30oC. The prevalence of low temperature and high humidity causes severe infestation of diseases.
Tomato is warm season crop. Grows well is those retain that are free from frost. It can't be grown successfully in places of higher rainfall. Temperature after tomato crops in following ways.
1. Optimum temperature for seed germination is 26 to 320C.
2. The optimum temperature required for its cultivation is 15 - 270C. At higher temperature its blossoms drops off. The damages great when high temp is combined with dry wind. It will result in the failure of fruit set due to drying of stigmatic liquid.
3. Colour development: In tomato red colour is due the pigment Lycopene. Lycopene is highest at 18 to 260C while production of this pigment drops off rapidly above 300C and 'nil' above 400C.
4. Carothe is developed rapidly at high temperature.
5. If fruits exposed to direct sunlight, their tops may turn whitish yellow & become leathery in texture. This is common in late varieties during summer season. This condition is known as sun - scald.
6. A warm, sunny weather is most suited for proper ripening, colour, quality & high yield that tomatoes be grown in dry areas under irrigation.
Mexico-
Land north of the 24th parallel experiences cooler temperatures during the winter months. South of the 24th parallel temperatures are fairly constant year round and vary solely by elevation.
Areas in the southern part with elevations up 1000 meters (the southern parts of both coastal plains as well as the Yucatan Peninsula) have a yearly medium temperature between 24 oC and 28 oC.
Temperatures here remain high throughout the year, with only 5 oC difference between summer and winter medium temperatures.
Although low-lying areas north of the 24th parallel are hot and humid during the summer, they generally have lower yearly temperatures averages (20 oC – 24 oC) because of more moderate conditions during the winter.
Between 1,000 and 2,000 metres, one encounters yearly average temperatures between 16 oC and 20 oC.
Areas at this elevations south of the 24th parallel have relatively constant temperatures, whereas more northerly locations experience sizable seasonal variations.
Above 2,000 meters, temperatures can drop as low as an average yearly range between 8 oC and 12 oC. Mexico City, at 2,300 meters, has a yearly medium temperature of 15 oC with pleasant summers and mild winters.
