In the Age of Kali, the saṅkīrtana-yajña (the chanting of the names of God) is recommended by the Vedic scriptures, and this transcendental system was introduced by Lord Caitanya for the deliverance of all men in this age. Saṅkīrtana-yajña and Kṛṣṇa consciousness go well together. Lord Kṛṣṇa in His devotional form (as Lord Caitanya) is mentioned in the Śrīmad-Bhāgavatam (11.5.32) as follows, with special reference to the saṅkīrtana-yajña:
kṛṣṇa-varṇaṁ tviṣākṛṣṇaṁ
sāṅgopāṅgāstra-pārṣadam
yajñaiḥ saṅkīrtana-prāyair
yajanti hi su-medhasaḥ
"In this Age of Kali, people who are endowed with sufficient intelligence will worship the Lord, who is accompanied by His associates, by performance of saṅkīrtana-yajña." Other yajñas prescribed in the Vedic literatures are not easy to perform in this Age of Kali, but the saṅkīrtana-yajña is easy and sublime for all purposes, as recommended in Bhagavad-gītā also (9.14).
(Bhagavad-Gita--3:10--purport).

Sacrifice is another item to be performed by the householders, because sacrifices require a large amount of money. Those in other orders of life, namely brahmacarya, vānaprastha and sannyāsa, have no money; they live by begging. So performance of different types of sacrifice is meant for the householders. They should perform agni-hotra sacrifices as enjoined in the Vedic literature, but such sacrifices at the present moment are very expensive, and it is not possible for any householder to perform them. The best sacrifice recommended in this age is called saṅkīrtana-yajña. This saṅkīrtana-yajña, the chanting of Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare, is the best and most inexpensive sacrifice; everyone can adopt it and derive benefit.
(Bhagavad-Gita--16:1-3--purport).

Persons who are engaged in fruitive activities for sense enjoyment must perform the prescribed sacrifices because that is the only means to get free from the reaction of all sins committed by fruitive workers. Sacrifice is the means for counteracting such accumulated sins. The demigods are pleased when such sacrifices are performed, just as prison officers are satisfied when the prisoners are turned into obedient subjects. Lord Caitanya, however, has recommended only one yajña, or sacrifice, called the saṅkīrtana-yajña, the chanting of Hare Kṛṣṇa, in which everyone can take part. Thus both devotees and fruitive workers can derive equal benefit from the performances of saṅkīrtana-yajña.
(Srimad Bhagavatam--1:16:20).

The basic principle of religion is truthfulness, and the ultimate goal of all religions is to satisfy the Lord. In this age of Kali, the greatest common formula of sacrifice is the saṅkīrtana-yajña. That is the opinion of the experts who know how to propagate the process of yajña. Lord Caitanya preached this method of yajña, and it is understood from this verse that the sacrificial method of saṅkīrtana-yajña may be performed anywhere and everywhere in order to drive away the personality of Kali and save human society from falling prey to the influence of the age.
(Srimad Bhagavatam--1:17:33--purport).

In the Śrīmad-Bhāgavatam it is clearly stated that in this age of Kali the only successful performance of yajña, or sacrifice, is yajñaiḥ saṅkīrtana-prāyaiḥ: the best type of sacrifice is simply to chant Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. This yajña is offered before the form of Lord Caitanya, as other yajñas are offered before the form of Lord Viṣṇu. These recommendations are found in the Eleventh Canto of the Śrīmad-Bhāgavatam. Moreover, this yajña performance confirms that Lord Caitanya Mahāprabhu is Viṣṇu Himself. As Lord Viṣṇu appeared at the Dakṣa yajña long, long ago, Lord Caitanya has appeared in this age to accept our saṅkīrtana-yajña.
(Srimad Bhagavatam----4:7:41--purport).

So that rainfall will be regulated, humanity should perform yajñas, sacrifices. Yajñas were previously performed with offerings of oblations of ghee and food grains, but in this age, of course, this is no longer possible, for the production of ghee and food grains has diminished because of the sinful life of human society. However, people should take to Kṛṣṇa consciousness and chant the Hare Kṛṣṇa mantra, as recommended in the śāstras (yajñaiḥ saṅkīrtana-prāyair yajanti hi sumedhasaḥ (SB-11:5:32)). If people throughout the world take to the Kṛṣṇa consciousness movement and chant the easy sound vibration of the transcendental name and fame of the Supreme Personality of Godhead, there will be no scarcity of rainfall; consequently food grains, fruits and flowers will be properly produced, and all the necessities of life will be easily obtained.
(Srimad Bhagavatam---7:14:7--purport).