functions.php

function wc_subscriptions_custom_price_string( $pricestring ) {
    global $product;

    $products_to_change = array( 45, 90, 238 );

    if ( in_array( $product->id, $products_to_change ) ) {
        $pricestring = str_replace( 'every 3 months', 'per season', $pricestring );
    }

    return $pricestring;
}
add_filter( 'woocommerce_subscriptions_product_price_string', 'wc_subscriptions_custom_price_string' );