vārāhi is one of the mātṛkā devis , a group of goddesses who are either seven or eight according to the text concerned. The usually accepted lot is Brahmani, Maheshvari, Kaumari, Vaishnavi, Varahi, Indrani, Chamunda. There are different stories about these heptapad as well as of each of these.
vārāhi, to put it simply, is the female form of the boar (varaaha) avataara. devi māhātmyam, mārkaṇḍeya purāṇam, vāmana purāṇam, varāha purāṇa, matsyapurāṇa, are some of the scriptures which refer to vārāhi. The origin, exploits and miscellaneous details about vārāhi differ from one text to another. (
http://en.wikipedia.org/wiki/Varahi)It will, therefore, be clear to any ordinary reader even, that vārāhi is like a stop-gap goddess, brought in according to the convenience and imaginative faculties of the person who wrote each of these texts.
Now, coming to navarātris : the seasons according to our tradition are six and there are five navarātris - vasanta, grīṣma (āṣāḍha), śarad, hemanta(pauṣa), śiśira (māgha). The only ṛtu in which navarātri is not prescribed is the varṣaṛtu or rainy season, and the reason is obvious-people would have found it very difficult to assemble and celebrate plus, the rainy season comes in the cāturmāsya period when austerities are supposed to be observed even otherwise. Roughly this cāturmāsya denotes sun's transit of the southern part of the celestial equator (dakṣiṇāyana) when the old vedic people living in the Ganga-Yamuna Doab would have felt the change of weather from hot to cold, and might have resorted to the austerities in order to brace themselves up to face the coming winter.
The navarātri starts with the first day after new moon and extends upto the ninth day during the bright half. Hindu lunar months ommenced on the first day after new moon or full moon according to the custom followed in different regions/ different groups. Thus for those who reckoned their month from the first day after new moon, navarātris fall at the commencement of the month. In the National Calendar the months are reckoned in a different way; it is a solar calendar though it borrows the ancient month names.
Despite whatever the scriptures may say about vārāhi navarātri or any navarātri for that matter, and its results etc., I think only the vasanta navarātri had been observed from the ancient past; the rest are later fabrications. vārāhi navarātri is important to the Tantriks who worship her at night through vāma mārga practices scuh as what the coḷī mārgis observe.
Since you seem to be very keen on observing the festival, given below are the gems of advice which I found in this webpage (
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Varahi Sadhana
During these ashadha navaratri , varahi has to be worshipped at each night with potatoes, pomegranate fruits, lotus, nut varieties, milk pudding, honey and madhubarka.
Iniciates can offer buffalo milk mixed with brown sugar,saffron, elaichi,lavangka,
For wealth one has to do archana with red lotus or red orleander flower.
For vaak siddhi, citta suddhi , archana has to be done with white lotus or white orleander.
For peace of mind, varahi must be worshipped with jasmine flowers.
The tantra sastra says that sree varahi will bless the sadhaka with mountains of emerald (maragata ratna) if the sadhaka does archana with pomegranate fillings. This simply means the sadhaka will be blessed with everlasting sowbagya and aiswarya.
Worshipping varahi with pomegranate flowers blesses one with love and affection among family and friends. Even separated couples will get reunited.
For shatru nashan varahi devi must be worshipped with blue lotus, or nilotphala flower.
By worshipping varahi with red flowers at night, all kinds of graham doshas and fears are removed.
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The fifth day of ashadha navaratri is the most important day . Its known as ashadha panchami. This is the most important night of varahi. On this day all devi sadhakas should worship amba varahi at midnight. Its believed that amba varahi appears on this night and blesses the person who worships her with her grace. All kinds of difficulties are removed by varahi's grace. Ashadha panchami is the crowning glory of this navaratri. The tantras says that Maha Varahi manifested on this day at midnight as siddha panchami devi.
Chanting varahi kavaca, varahi anugrahashtaka, varahi nigrahaashtaka, varahi sahasranama, varahi trishati , varahi ashtotra satha namavali, or the aadhi varahi stotra attracts varahi's grace.
FOR INICIATES (
sic)
Iniciates can perform varahi avarana puja / homa.
This is the most auspicious time to do purascarana of of laghu vartali, swapna varahi , ashwaruudha , and maha varahi mantras.
Tarpana for varahi mantras should be done with tender coconut water only . Coconut water should never be used!
Suvashini puja and suvashini bojana are very important in varahi purascarana.